* [Qemu-devel] [PATCH v6 0/7] vhost-user-blk: Add support for backend reconnecting
@ 2019-02-18 10:27 elohimes
2019-02-18 10:27 ` [Qemu-devel] [PATCH v6 1/7] vhost-user: Support transferring inflight buffer between qemu and backend elohimes
` (7 more replies)
0 siblings, 8 replies; 18+ messages in thread
From: elohimes @ 2019-02-18 10:27 UTC (permalink / raw)
To: mst, stefanha, marcandre.lureau, berrange, jasowang,
maxime.coquelin, yury-kotov, wrfsh
Cc: qemu-devel, zhangyu31, chaiwen, nixun, lilin24, Xie Yongji
From: Xie Yongji <xieyongji@baidu.com>
This patchset is aimed at supporting qemu to reconnect
vhost-user-blk backend after vhost-user-blk backend crash or
restart.
The patch 1 introduces two new messages VHOST_USER_GET_INFLIGHT_FD
and VHOST_USER_SET_INFLIGHT_FD to support transferring shared
buffer between qemu and backend.
The patch 2 deletes some redundant check in contrib/libvhost-user.c.
The patch 3,4 are the corresponding libvhost-user patches of
patch 1. Make libvhost-user support VHOST_USER_GET_INFLIGHT_FD
and VHOST_USER_SET_INFLIGHT_FD.
The patch 5 allows vhost-user-blk to use the two new messages
to get/set inflight buffer from/to backend.
The patch 6 supports vhost-user-blk to reconnect backend when
connection closed.
The patch 7 introduces VHOST_USER_PROTOCOL_F_SLAVE_SHMFD
to vhost-user-blk backend which is used to tell qemu that
we support reconnecting now.
To use it, we could start qemu with:
qemu-system-x86_64 \
-chardev socket,id=char0,path=/path/vhost.socket,reconnect=1, \
-device vhost-user-blk-pci,chardev=char0 \
and start vhost-user-blk backend with:
vhost-user-blk -b /path/file -s /path/vhost.socket
Then we can restart vhost-user-blk at any time during VM running.
V5 to V6:
- Document the layout in inflight buffer for packed virtqueue
- Rework the layout in inflight buffer for split virtqueue
- Remove version field in VhostUserInflight
- Add a patch to remove some redundant check in
contrib/libvhost-user.c
- Document more details in vhost-user.txt
V4 to V5:
- Drop patch that enables "nowait" option on client sockets
- Support resubmitting inflight I/O in order
- Make inflight I/O tracking more robust
- Remove align field and add queue size field in VhostUserInflight
- Document more details in vhost-user.txt
V3 to V4:
- Drop messages VHOST_USER_GET_SHM_SIZE and VHOST_USER_SET_SHM_FD
- Introduce two new messages VHOST_USER_GET_INFLIGHT_FD
and VHOST_USER_SET_INFLIGHT_FD
- Allocate inflight buffer in backend rather than in qemu
- Document a recommended format for inflight buffer
V2 to V3:
- Using exisiting wait/nowait options to control connection on
client sockets instead of introducing "disconnected" option.
- Support the case that vhost-user backend restart during initialzation
of vhost-user-blk device.
V1 to V2:
- Introduce "disconnected" option for chardev instead of reuse "wait"
option
- Support the case that QEMU starts before vhost-user backend
- Drop message VHOST_USER_SET_VRING_INFLIGHT
- Introduce two new messages VHOST_USER_GET_SHM_SIZE
and VHOST_USER_SET_SHM_FD
Xie Yongji (7):
vhost-user: Support transferring inflight buffer between qemu and
backend
libvhost-user: Remove unnecessary FD flag check for event file
descriptors
libvhost-user: Introduce vu_queue_map_desc()
libvhost-user: Support tracking inflight I/O in shared memory
vhost-user-blk: Add support to get/set inflight buffer
vhost-user-blk: Add support to reconnect backend
contrib/vhost-user-blk: enable inflight I/O tracking
Makefile | 2 +-
contrib/libvhost-user/libvhost-user.c | 400 ++++++++++++++++++++----
contrib/libvhost-user/libvhost-user.h | 58 ++++
contrib/vhost-user-blk/vhost-user-blk.c | 3 +-
docs/interop/vhost-user.txt | 264 ++++++++++++++++
hw/block/vhost-user-blk.c | 229 +++++++++++---
hw/virtio/vhost-user.c | 107 +++++++
hw/virtio/vhost.c | 96 ++++++
include/hw/virtio/vhost-backend.h | 10 +
include/hw/virtio/vhost-user-blk.h | 5 +
include/hw/virtio/vhost.h | 18 ++
11 files changed, 1084 insertions(+), 108 deletions(-)
--
2.17.1
^ permalink raw reply [flat|nested] 18+ messages in thread
* [Qemu-devel] [PATCH v6 1/7] vhost-user: Support transferring inflight buffer between qemu and backend
2019-02-18 10:27 [Qemu-devel] [PATCH v6 0/7] vhost-user-blk: Add support for backend reconnecting elohimes
@ 2019-02-18 10:27 ` elohimes
2019-02-21 17:27 ` Michael S. Tsirkin
2019-02-18 10:27 ` [Qemu-devel] [PATCH v6 2/7] libvhost-user: Remove unnecessary FD flag check for event file descriptors elohimes
` (6 subsequent siblings)
7 siblings, 1 reply; 18+ messages in thread
From: elohimes @ 2019-02-18 10:27 UTC (permalink / raw)
To: mst, stefanha, marcandre.lureau, berrange, jasowang,
maxime.coquelin, yury-kotov, wrfsh
Cc: qemu-devel, zhangyu31, chaiwen, nixun, lilin24, Xie Yongji
From: Xie Yongji <xieyongji@baidu.com>
This patch introduces two new messages VHOST_USER_GET_INFLIGHT_FD
and VHOST_USER_SET_INFLIGHT_FD to support transferring a shared
buffer between qemu and backend.
Firstly, qemu uses VHOST_USER_GET_INFLIGHT_FD to get the
shared buffer from backend. Then qemu should send it back
through VHOST_USER_SET_INFLIGHT_FD each time we start vhost-user.
This shared buffer is used to track inflight I/O by backend.
Qemu should retrieve a new one when vm reset.
Signed-off-by: Xie Yongji <xieyongji@baidu.com>
Signed-off-by: Chai Wen <chaiwen@baidu.com>
Signed-off-by: Zhang Yu <zhangyu31@baidu.com>
---
docs/interop/vhost-user.txt | 264 ++++++++++++++++++++++++++++++
hw/virtio/vhost-user.c | 107 ++++++++++++
hw/virtio/vhost.c | 96 +++++++++++
include/hw/virtio/vhost-backend.h | 10 ++
include/hw/virtio/vhost.h | 18 ++
5 files changed, 495 insertions(+)
diff --git a/docs/interop/vhost-user.txt b/docs/interop/vhost-user.txt
index c2194711d9..61c6d0e415 100644
--- a/docs/interop/vhost-user.txt
+++ b/docs/interop/vhost-user.txt
@@ -142,6 +142,17 @@ Depending on the request type, payload can be:
Offset: a 64-bit offset of this area from the start of the
supplied file descriptor
+ * Inflight description
+ -----------------------------------------------------
+ | mmap size | mmap offset | num queues | queue size |
+ -----------------------------------------------------
+
+ mmap size: a 64-bit size of area to track inflight I/O
+ mmap offset: a 64-bit offset of this area from the start
+ of the supplied file descriptor
+ num queues: a 16-bit number of virtqueues
+ queue size: a 16-bit size of virtqueues
+
In QEMU the vhost-user message is implemented with the following struct:
typedef struct VhostUserMsg {
@@ -157,6 +168,7 @@ typedef struct VhostUserMsg {
struct vhost_iotlb_msg iotlb;
VhostUserConfig config;
VhostUserVringArea area;
+ VhostUserInflight inflight;
};
} QEMU_PACKED VhostUserMsg;
@@ -175,6 +187,7 @@ the ones that do:
* VHOST_USER_GET_PROTOCOL_FEATURES
* VHOST_USER_GET_VRING_BASE
* VHOST_USER_SET_LOG_BASE (if VHOST_USER_PROTOCOL_F_LOG_SHMFD)
+ * VHOST_USER_GET_INFLIGHT_FD (if VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD)
[ Also see the section on REPLY_ACK protocol extension. ]
@@ -188,6 +201,7 @@ in the ancillary data:
* VHOST_USER_SET_VRING_CALL
* VHOST_USER_SET_VRING_ERR
* VHOST_USER_SET_SLAVE_REQ_FD
+ * VHOST_USER_SET_INFLIGHT_FD (if VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD)
If Master is unable to send the full message or receives a wrong reply it will
close the connection. An optional reconnection mechanism can be implemented.
@@ -382,6 +396,235 @@ If VHOST_USER_PROTOCOL_F_SLAVE_SEND_FD protocol feature is negotiated,
slave can send file descriptors (at most 8 descriptors in each message)
to master via ancillary data using this fd communication channel.
+Inflight I/O tracking
+---------------------
+
+To support reconnecting after restart or crash, slave may need to resubmit
+inflight I/Os. If virtqueue is processed in order, we can easily achieve
+that by getting the inflight descriptors from descriptor table (split virtqueue)
+or descriptor ring (packed virtqueue). However, it can't work when we process
+descriptors out-of-order because some entries which store the information of
+inflight descriptors in available ring (split virtqueue) or descriptor
+ring (packed virtqueue) might be overrided by new entries. To solve this
+problem, slave need to allocate an extra buffer to store this information of inflight
+descriptors and share it with master for persistent. VHOST_USER_GET_INFLIGHT_FD and
+VHOST_USER_SET_INFLIGHT_FD are used to transfer this buffer between master
+and slave. And the format of this buffer is described below:
+
+-------------------------------------------------------
+| queue0 region | queue1 region | ... | queueN region |
+-------------------------------------------------------
+
+N is the number of available virtqueues. Slave could get it from num queues
+field of VhostUserInflight.
+
+For split virtqueue, queue region can be implemented as:
+
+typedef struct DescStateSplit {
+ /* Indicate whether this descriptor is inflight or not.
+ * Only available for head-descriptor. */
+ uint8_t inflight;
+
+ /* Padding */
+ uint8_t padding;
+
+ /* Link to the last processed entry */
+ uint16_t next;
+} DescStateSplit;
+
+typedef struct QueueRegionSplit {
+ /* The feature flags of this region. Now it's initialized to 0. */
+ uint64_t features;
+
+ /* The version of this region. It's 1 currently.
+ * Zero value indicates an uninitialized buffer */
+ uint16_t version;
+
+ /* The size of DescStateSplit array. It's equal to the virtqueue
+ * size. Slave could get it from queue size field of VhostUserInflight. */
+ uint16_t desc_num;
+
+ /* The head of processed DescStateSplit entry list */
+ uint16_t process_head;
+
+ /* Storing the idx value of used ring */
+ uint16_t used_idx;
+
+ /* Used to track the state of each descriptor in descriptor table */
+ DescStateSplit desc[0];
+} QueueRegionSplit;
+
+To track inflight I/O, the queue region should be processed as follows:
+
+When receiving available buffers from the driver:
+
+ 1. Get the next available head-descriptor index from available ring, i
+
+ 2. Set desc[i].inflight to 1
+
+When supplying used buffers to the driver:
+
+ 1. Get corresponding used head-descriptor index, i
+
+ 2. Set desc[i].next to process_head
+
+ 3. Set process_head to i
+
+ 4. Steps 1,2,3 may be performed repeatedly if batching is possible
+
+ 5. Increase the idx value of used ring by the size of the batch
+
+ 6. Set the inflight field of each DescStateSplit entry in the batch to 0
+
+ 7. Set used_idx to the idx value of used ring
+
+When reconnecting:
+
+ 1. If the value of used_idx does not match the idx value of used ring,
+
+ (a) Subtract the value of used_idx from the idx value of used ring to get
+ the number of in-progress DescStateSplit entries
+
+ (b) Set the inflight field of the in-progress DescStateSplit entries which
+ start from process_head to 0
+
+ (c) Set used_idx to the idx value of used ring
+
+ 2. Resubmit each inflight DescStateSplit entry
+
+For packed virtqueue, queue region can be implemented as:
+
+typedef struct DescStatePacked {
+ /* Indicate whether this descriptor is inflight or not.
+ * Only available for head-descriptor. */
+ uint8_t inflight;
+
+ /* Padding */
+ uint8_t padding;
+
+ /* Link to the next free entry */
+ uint16_t next;
+
+ /* Link to the last entry of descriptor list.
+ * Only available for head-descriptor. */
+ uint16_t last;
+
+ /* The length of descriptor list.
+ * Only available for head-descriptor. */
+ uint16_t num;
+
+ /* The buffer id */
+ uint16_t id;
+
+ /* The descriptor flags */
+ uint16_t flags;
+
+ /* The buffer length */
+ uint32_t len;
+
+ /* The buffer address */
+ uint64_t addr;
+} DescStatePacked;
+
+typedef struct QueueRegionPacked {
+ /* The feature flags of this region. Now it's initialized to 0. */
+ uint64_t features;
+
+ /* The version of this region. It's 1 currently.
+ * Zero value indicates an uninitialized buffer */
+ uint16_t version;
+
+ /* The size of DescStatePacked array. It's equal to the virtqueue
+ * size. Slave could get it from queue size field of VhostUserInflight. */
+ uint16_t desc_num;
+
+ /* The head of free DescStatePacked entry list */
+ uint16_t free_head;
+
+ /* The old head of free DescStatePacked entry list */
+ uint16_t old_free_head;
+
+ /* The used index of descriptor ring */
+ uint16_t used_idx;
+
+ /* The old used index of descriptor ring */
+ uint16_t old_used_idx;
+
+ /* Device ring wrap counter */
+ uint8_t used_wrap_counter;
+
+ /* The old device ring wrap counter */
+ uint8_t old_used_wrap_counter;
+
+ /* Padding */
+ uint8_t padding[7];
+
+ /* Used to track the state of each descriptor fetched from descriptor ring */
+ DescStatePacked desc[0];
+} QueueRegionPacked;
+
+To track inflight I/O, the queue region should be processed as follows:
+
+When receiving available buffers from the driver:
+
+ 1. Get the next available descriptor entry from descriptor ring, d
+
+ 2. If d is head descriptor,
+
+ (a) Set desc[old_free_head].num to 0
+
+ (b) Set desc[old_free_head].inflight to 1
+
+ 3. If d is last descriptor, set desc[old_free_head].last to free_head
+
+ 4. Increase desc[old_free_head].num by 1
+
+ 5. Set desc[free_head].addr, desc[free_head].len, desc[free_head].flags,
+ desc[free_head].id to d.addr, d.len, d.flags, d.id
+
+ 6. Set free_head to desc[free_head].next
+
+ 7. If d is last descriptor, set old_free_head to free_head
+
+When supplying used buffers to the driver:
+
+ 1. Get corresponding used head-descriptor entry from descriptor ring, d
+
+ 2. Get corresponding DescStatePacked entry, e
+
+ 3. Set desc[e.last].next to free_head
+
+ 4. Set free_head to the index of e
+
+ 5. Steps 1,2,3,4 may be performed repeatedly if batching is possible
+
+ 6. Increase used_idx by the size of the batch and update used_wrap_counter if needed
+
+ 7. Update d.flags
+
+ 8. Set the inflight field of each head DescStatePacked entry in the batch to 0
+
+ 9. Set old_free_head, old_used_idx, old_used_wrap_counter to free_head, used_idx,
+ used_wrap_counter
+
+When reconnecting:
+
+ 1. If used_idx does not match old_used_idx,
+
+ (a) Get the next descriptor ring entry through old_used_idx, d
+
+ (b) Use old_used_wrap_counter to calculate the available flags
+
+ (c) If d.flags is not equal to the calculated flags value, set old_free_head,
+ old_used_idx, old_used_wrap_counter to free_head, used_idx, used_wrap_counter
+
+ 2. Set free_head, used_idx, used_wrap_counter to old_free_head, old_used_idx,
+ old_used_wrap_counter
+
+ 3. Set the inflight field of each free DescStatePacked entry to 0
+
+ 4. Resubmit each inflight DescStatePacked entry
+
Protocol features
-----------------
@@ -397,6 +640,7 @@ Protocol features
#define VHOST_USER_PROTOCOL_F_CONFIG 9
#define VHOST_USER_PROTOCOL_F_SLAVE_SEND_FD 10
#define VHOST_USER_PROTOCOL_F_HOST_NOTIFIER 11
+#define VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD 12
Master message types
--------------------
@@ -761,6 +1005,26 @@ Master message types
was previously sent.
The value returned is an error indication; 0 is success.
+ * VHOST_USER_GET_INFLIGHT_FD
+ Id: 31
+ Equivalent ioctl: N/A
+ Master payload: inflight description
+
+ When VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD protocol feature has been
+ successfully negotiated, this message is submitted by master to get
+ a shared buffer from slave. The shared buffer will be used to track
+ inflight I/O by slave. QEMU should retrieve a new one when vm reset.
+
+ * VHOST_USER_SET_INFLIGHT_FD
+ Id: 32
+ Equivalent ioctl: N/A
+ Master payload: inflight description
+
+ When VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD protocol feature has been
+ successfully negotiated, this message is submitted by master to send
+ the shared inflight buffer back to slave so that slave could get
+ inflight I/O after a crash or restart.
+
Slave message types
-------------------
diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
index 564a31d12c..21a81998ba 100644
--- a/hw/virtio/vhost-user.c
+++ b/hw/virtio/vhost-user.c
@@ -52,6 +52,7 @@ enum VhostUserProtocolFeature {
VHOST_USER_PROTOCOL_F_CONFIG = 9,
VHOST_USER_PROTOCOL_F_SLAVE_SEND_FD = 10,
VHOST_USER_PROTOCOL_F_HOST_NOTIFIER = 11,
+ VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD = 12,
VHOST_USER_PROTOCOL_F_MAX
};
@@ -89,6 +90,8 @@ typedef enum VhostUserRequest {
VHOST_USER_POSTCOPY_ADVISE = 28,
VHOST_USER_POSTCOPY_LISTEN = 29,
VHOST_USER_POSTCOPY_END = 30,
+ VHOST_USER_GET_INFLIGHT_FD = 31,
+ VHOST_USER_SET_INFLIGHT_FD = 32,
VHOST_USER_MAX
} VhostUserRequest;
@@ -147,6 +150,13 @@ typedef struct VhostUserVringArea {
uint64_t offset;
} VhostUserVringArea;
+typedef struct VhostUserInflight {
+ uint64_t mmap_size;
+ uint64_t mmap_offset;
+ uint16_t num_queues;
+ uint16_t queue_size;
+} VhostUserInflight;
+
typedef struct {
VhostUserRequest request;
@@ -169,6 +179,7 @@ typedef union {
VhostUserConfig config;
VhostUserCryptoSession session;
VhostUserVringArea area;
+ VhostUserInflight inflight;
} VhostUserPayload;
typedef struct VhostUserMsg {
@@ -1739,6 +1750,100 @@ static bool vhost_user_mem_section_filter(struct vhost_dev *dev,
return result;
}
+static int vhost_user_get_inflight_fd(struct vhost_dev *dev,
+ uint16_t queue_size,
+ struct vhost_inflight *inflight)
+{
+ void *addr;
+ int fd;
+ struct vhost_user *u = dev->opaque;
+ CharBackend *chr = u->user->chr;
+ VhostUserMsg msg = {
+ .hdr.request = VHOST_USER_GET_INFLIGHT_FD,
+ .hdr.flags = VHOST_USER_VERSION,
+ .payload.inflight.num_queues = dev->nvqs,
+ .payload.inflight.queue_size = queue_size,
+ .hdr.size = sizeof(msg.payload.inflight),
+ };
+
+ if (!virtio_has_feature(dev->protocol_features,
+ VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD)) {
+ return 0;
+ }
+
+ if (vhost_user_write(dev, &msg, NULL, 0) < 0) {
+ return -1;
+ }
+
+ if (vhost_user_read(dev, &msg) < 0) {
+ return -1;
+ }
+
+ if (msg.hdr.request != VHOST_USER_GET_INFLIGHT_FD) {
+ error_report("Received unexpected msg type. "
+ "Expected %d received %d",
+ VHOST_USER_GET_INFLIGHT_FD, msg.hdr.request);
+ return -1;
+ }
+
+ if (msg.hdr.size != sizeof(msg.payload.inflight)) {
+ error_report("Received bad msg size.");
+ return -1;
+ }
+
+ if (!msg.payload.inflight.mmap_size) {
+ return 0;
+ }
+
+ fd = qemu_chr_fe_get_msgfd(chr);
+ if (fd < 0) {
+ error_report("Failed to get mem fd");
+ return -1;
+ }
+
+ addr = mmap(0, msg.payload.inflight.mmap_size, PROT_READ | PROT_WRITE,
+ MAP_SHARED, fd, msg.payload.inflight.mmap_offset);
+
+ if (addr == MAP_FAILED) {
+ error_report("Failed to mmap mem fd");
+ close(fd);
+ return -1;
+ }
+
+ inflight->addr = addr;
+ inflight->fd = fd;
+ inflight->size = msg.payload.inflight.mmap_size;
+ inflight->offset = msg.payload.inflight.mmap_offset;
+ inflight->queue_size = queue_size;
+
+ return 0;
+}
+
+static int vhost_user_set_inflight_fd(struct vhost_dev *dev,
+ struct vhost_inflight *inflight)
+{
+ VhostUserMsg msg = {
+ .hdr.request = VHOST_USER_SET_INFLIGHT_FD,
+ .hdr.flags = VHOST_USER_VERSION,
+ .payload.inflight.mmap_size = inflight->size,
+ .payload.inflight.mmap_offset = inflight->offset,
+ .payload.inflight.num_queues = dev->nvqs,
+ .payload.inflight.queue_size = inflight->queue_size,
+ .hdr.size = sizeof(msg.payload.inflight),
+ };
+
+ if (!virtio_has_feature(dev->protocol_features,
+ VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD)) {
+ return 0;
+ }
+
+ if (vhost_user_write(dev, &msg, &inflight->fd, 1) < 0) {
+ return -1;
+ }
+
+ return 0;
+}
+
VhostUserState *vhost_user_init(void)
{
VhostUserState *user = g_new0(struct VhostUserState, 1);
@@ -1790,4 +1895,6 @@ const VhostOps user_ops = {
.vhost_crypto_create_session = vhost_user_crypto_create_session,
.vhost_crypto_close_session = vhost_user_crypto_close_session,
.vhost_backend_mem_section_filter = vhost_user_mem_section_filter,
+ .vhost_get_inflight_fd = vhost_user_get_inflight_fd,
+ .vhost_set_inflight_fd = vhost_user_set_inflight_fd,
};
diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index 569c4053ea..8db1a855eb 100644
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -1481,6 +1481,102 @@ void vhost_dev_set_config_notifier(struct vhost_dev *hdev,
hdev->config_ops = ops;
}
+void vhost_dev_free_inflight(struct vhost_inflight *inflight)
+{
+ if (inflight->addr) {
+ qemu_memfd_free(inflight->addr, inflight->size, inflight->fd);
+ inflight->addr = NULL;
+ inflight->fd = -1;
+ }
+}
+
+static int vhost_dev_resize_inflight(struct vhost_inflight *inflight,
+ uint64_t new_size)
+{
+ Error *err = NULL;
+ int fd = -1;
+ void *addr = qemu_memfd_alloc("vhost-inflight", new_size,
+ F_SEAL_GROW | F_SEAL_SHRINK | F_SEAL_SEAL,
+ &fd, &err);
+
+ if (err) {
+ error_report_err(err);
+ return -1;
+ }
+
+ vhost_dev_free_inflight(inflight);
+ inflight->offset = 0;
+ inflight->addr = addr;
+ inflight->fd = fd;
+ inflight->size = new_size;
+
+ return 0;
+}
+
+void vhost_dev_save_inflight(struct vhost_inflight *inflight, QEMUFile *f)
+{
+ if (inflight->addr) {
+ qemu_put_be64(f, inflight->size);
+ qemu_put_be16(f, inflight->queue_size);
+ qemu_put_buffer(f, inflight->addr, inflight->size);
+ } else {
+ qemu_put_be64(f, 0);
+ }
+}
+
+int vhost_dev_load_inflight(struct vhost_inflight *inflight, QEMUFile *f)
+{
+ uint64_t size;
+
+ size = qemu_get_be64(f);
+ if (!size) {
+ return 0;
+ }
+
+ if (inflight->size != size) {
+ if (vhost_dev_resize_inflight(inflight, size)) {
+ return -1;
+ }
+ }
+ inflight->queue_size = qemu_get_be16(f);
+
+ qemu_get_buffer(f, inflight->addr, size);
+
+ return 0;
+}
+
+int vhost_dev_set_inflight(struct vhost_dev *dev,
+ struct vhost_inflight *inflight)
+{
+ int r;
+
+ if (dev->vhost_ops->vhost_set_inflight_fd && inflight->addr) {
+ r = dev->vhost_ops->vhost_set_inflight_fd(dev, inflight);
+ if (r) {
+ VHOST_OPS_DEBUG("vhost_set_inflight_fd failed");
+ return -errno;
+ }
+ }
+
+ return 0;
+}
+
+int vhost_dev_get_inflight(struct vhost_dev *dev, uint16_t queue_size,
+ struct vhost_inflight *inflight)
+{
+ int r;
+
+ if (dev->vhost_ops->vhost_get_inflight_fd) {
+ r = dev->vhost_ops->vhost_get_inflight_fd(dev, queue_size, inflight);
+ if (r) {
+ VHOST_OPS_DEBUG("vhost_get_inflight_fd failed");
+ return -errno;
+ }
+ }
+
+ return 0;
+}
+
/* Host notifiers must be enabled at this point. */
int vhost_dev_start(struct vhost_dev *hdev, VirtIODevice *vdev)
{
diff --git a/include/hw/virtio/vhost-backend.h b/include/hw/virtio/vhost-backend.h
index 81283ec50f..d6632a18e6 100644
--- a/include/hw/virtio/vhost-backend.h
+++ b/include/hw/virtio/vhost-backend.h
@@ -25,6 +25,7 @@ typedef enum VhostSetConfigType {
VHOST_SET_CONFIG_TYPE_MIGRATION = 1,
} VhostSetConfigType;
+struct vhost_inflight;
struct vhost_dev;
struct vhost_log;
struct vhost_memory;
@@ -104,6 +105,13 @@ typedef int (*vhost_crypto_close_session_op)(struct vhost_dev *dev,
typedef bool (*vhost_backend_mem_section_filter_op)(struct vhost_dev *dev,
MemoryRegionSection *section);
+typedef int (*vhost_get_inflight_fd_op)(struct vhost_dev *dev,
+ uint16_t queue_size,
+ struct vhost_inflight *inflight);
+
+typedef int (*vhost_set_inflight_fd_op)(struct vhost_dev *dev,
+ struct vhost_inflight *inflight);
+
typedef struct VhostOps {
VhostBackendType backend_type;
vhost_backend_init vhost_backend_init;
@@ -142,6 +150,8 @@ typedef struct VhostOps {
vhost_crypto_create_session_op vhost_crypto_create_session;
vhost_crypto_close_session_op vhost_crypto_close_session;
vhost_backend_mem_section_filter_op vhost_backend_mem_section_filter;
+ vhost_get_inflight_fd_op vhost_get_inflight_fd;
+ vhost_set_inflight_fd_op vhost_set_inflight_fd;
} VhostOps;
extern const VhostOps user_ops;
diff --git a/include/hw/virtio/vhost.h b/include/hw/virtio/vhost.h
index a7f449fa87..619498c8f4 100644
--- a/include/hw/virtio/vhost.h
+++ b/include/hw/virtio/vhost.h
@@ -7,6 +7,15 @@
#include "exec/memory.h"
/* Generic structures common for any vhost based device. */
+
+struct vhost_inflight {
+ int fd;
+ void *addr;
+ uint64_t size;
+ uint64_t offset;
+ uint16_t queue_size;
+};
+
struct vhost_virtqueue {
int kick;
int call;
@@ -120,4 +129,13 @@ int vhost_dev_set_config(struct vhost_dev *dev, const uint8_t *data,
*/
void vhost_dev_set_config_notifier(struct vhost_dev *dev,
const VhostDevConfigOps *ops);
+
+void vhost_dev_reset_inflight(struct vhost_inflight *inflight);
+void vhost_dev_free_inflight(struct vhost_inflight *inflight);
+void vhost_dev_save_inflight(struct vhost_inflight *inflight, QEMUFile *f);
+int vhost_dev_load_inflight(struct vhost_inflight *inflight, QEMUFile *f);
+int vhost_dev_set_inflight(struct vhost_dev *dev,
+ struct vhost_inflight *inflight);
+int vhost_dev_get_inflight(struct vhost_dev *dev, uint16_t queue_size,
+ struct vhost_inflight *inflight);
#endif
--
2.17.1
^ permalink raw reply related [flat|nested] 18+ messages in thread
* [Qemu-devel] [PATCH v6 2/7] libvhost-user: Remove unnecessary FD flag check for event file descriptors
2019-02-18 10:27 [Qemu-devel] [PATCH v6 0/7] vhost-user-blk: Add support for backend reconnecting elohimes
2019-02-18 10:27 ` [Qemu-devel] [PATCH v6 1/7] vhost-user: Support transferring inflight buffer between qemu and backend elohimes
@ 2019-02-18 10:27 ` elohimes
2019-02-18 10:27 ` [Qemu-devel] [PATCH v6 3/7] libvhost-user: Introduce vu_queue_map_desc() elohimes
` (5 subsequent siblings)
7 siblings, 0 replies; 18+ messages in thread
From: elohimes @ 2019-02-18 10:27 UTC (permalink / raw)
To: mst, stefanha, marcandre.lureau, berrange, jasowang,
maxime.coquelin, yury-kotov, wrfsh
Cc: qemu-devel, zhangyu31, chaiwen, nixun, lilin24, Xie Yongji
From: Xie Yongji <xieyongji@baidu.com>
The vu_check_queue_msg_file() has checked the FD flag. So let's
delete the redundant check after it.
Signed-off-by: Xie Yongji <xieyongji@baidu.com>
Signed-off-by: Zhang Yu <zhangyu31@baidu.com>
---
contrib/libvhost-user/libvhost-user.c | 14 ++++----------
1 file changed, 4 insertions(+), 10 deletions(-)
diff --git a/contrib/libvhost-user/libvhost-user.c b/contrib/libvhost-user/libvhost-user.c
index 3f14b4138b..16fec3a3fd 100644
--- a/contrib/libvhost-user/libvhost-user.c
+++ b/contrib/libvhost-user/libvhost-user.c
@@ -907,10 +907,8 @@ vu_set_vring_kick_exec(VuDev *dev, VhostUserMsg *vmsg)
dev->vq[index].kick_fd = -1;
}
- if (!(vmsg->payload.u64 & VHOST_USER_VRING_NOFD_MASK)) {
- dev->vq[index].kick_fd = vmsg->fds[0];
- DPRINT("Got kick_fd: %d for vq: %d\n", vmsg->fds[0], index);
- }
+ dev->vq[index].kick_fd = vmsg->fds[0];
+ DPRINT("Got kick_fd: %d for vq: %d\n", vmsg->fds[0], index);
dev->vq[index].started = true;
if (dev->iface->queue_set_started) {
@@ -995,9 +993,7 @@ vu_set_vring_call_exec(VuDev *dev, VhostUserMsg *vmsg)
dev->vq[index].call_fd = -1;
}
- if (!(vmsg->payload.u64 & VHOST_USER_VRING_NOFD_MASK)) {
- dev->vq[index].call_fd = vmsg->fds[0];
- }
+ dev->vq[index].call_fd = vmsg->fds[0];
DPRINT("Got call_fd: %d for vq: %d\n", vmsg->fds[0], index);
@@ -1020,9 +1016,7 @@ vu_set_vring_err_exec(VuDev *dev, VhostUserMsg *vmsg)
dev->vq[index].err_fd = -1;
}
- if (!(vmsg->payload.u64 & VHOST_USER_VRING_NOFD_MASK)) {
- dev->vq[index].err_fd = vmsg->fds[0];
- }
+ dev->vq[index].err_fd = vmsg->fds[0];
return false;
}
--
2.17.1
^ permalink raw reply related [flat|nested] 18+ messages in thread
* [Qemu-devel] [PATCH v6 3/7] libvhost-user: Introduce vu_queue_map_desc()
2019-02-18 10:27 [Qemu-devel] [PATCH v6 0/7] vhost-user-blk: Add support for backend reconnecting elohimes
2019-02-18 10:27 ` [Qemu-devel] [PATCH v6 1/7] vhost-user: Support transferring inflight buffer between qemu and backend elohimes
2019-02-18 10:27 ` [Qemu-devel] [PATCH v6 2/7] libvhost-user: Remove unnecessary FD flag check for event file descriptors elohimes
@ 2019-02-18 10:27 ` elohimes
2019-02-18 10:27 ` [Qemu-devel] [PATCH v6 4/7] libvhost-user: Support tracking inflight I/O in shared memory elohimes
` (4 subsequent siblings)
7 siblings, 0 replies; 18+ messages in thread
From: elohimes @ 2019-02-18 10:27 UTC (permalink / raw)
To: mst, stefanha, marcandre.lureau, berrange, jasowang,
maxime.coquelin, yury-kotov, wrfsh
Cc: qemu-devel, zhangyu31, chaiwen, nixun, lilin24, Xie Yongji
From: Xie Yongji <xieyongji@baidu.com>
Introduce vu_queue_map_desc() which should be
independent with vu_queue_pop();
Signed-off-by: Xie Yongji <xieyongji@baidu.com>
Signed-off-by: Zhang Yu <zhangyu31@baidu.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
---
contrib/libvhost-user/libvhost-user.c | 88 ++++++++++++++++-----------
1 file changed, 51 insertions(+), 37 deletions(-)
diff --git a/contrib/libvhost-user/libvhost-user.c b/contrib/libvhost-user/libvhost-user.c
index 16fec3a3fd..ea0f414b6d 100644
--- a/contrib/libvhost-user/libvhost-user.c
+++ b/contrib/libvhost-user/libvhost-user.c
@@ -1847,49 +1847,20 @@ virtqueue_alloc_element(size_t sz,
return elem;
}
-void *
-vu_queue_pop(VuDev *dev, VuVirtq *vq, size_t sz)
+static void *
+vu_queue_map_desc(VuDev *dev, VuVirtq *vq, unsigned int idx, size_t sz)
{
- unsigned int i, head, max, desc_len;
+ struct vring_desc *desc = vq->vring.desc;
uint64_t desc_addr, read_len;
+ unsigned int desc_len;
+ unsigned int max = vq->vring.num;
+ unsigned int i = idx;
VuVirtqElement *elem;
- unsigned out_num, in_num;
+ unsigned int out_num = 0, in_num = 0;
struct iovec iov[VIRTQUEUE_MAX_SIZE];
struct vring_desc desc_buf[VIRTQUEUE_MAX_SIZE];
- struct vring_desc *desc;
int rc;
- if (unlikely(dev->broken) ||
- unlikely(!vq->vring.avail)) {
- return NULL;
- }
-
- if (vu_queue_empty(dev, vq)) {
- return NULL;
- }
- /* Needed after virtio_queue_empty(), see comment in
- * virtqueue_num_heads(). */
- smp_rmb();
-
- /* When we start there are none of either input nor output. */
- out_num = in_num = 0;
-
- max = vq->vring.num;
- if (vq->inuse >= vq->vring.num) {
- vu_panic(dev, "Virtqueue size exceeded");
- return NULL;
- }
-
- if (!virtqueue_get_head(dev, vq, vq->last_avail_idx++, &head)) {
- return NULL;
- }
-
- if (vu_has_feature(dev, VIRTIO_RING_F_EVENT_IDX)) {
- vring_set_avail_event(vq, vq->last_avail_idx);
- }
-
- i = head;
- desc = vq->vring.desc;
if (desc[i].flags & VRING_DESC_F_INDIRECT) {
if (desc[i].len % sizeof(struct vring_desc)) {
vu_panic(dev, "Invalid size for indirect buffer table");
@@ -1941,12 +1912,13 @@ vu_queue_pop(VuDev *dev, VuVirtq *vq, size_t sz)
} while (rc == VIRTQUEUE_READ_DESC_MORE);
if (rc == VIRTQUEUE_READ_DESC_ERROR) {
+ vu_panic(dev, "read descriptor error");
return NULL;
}
/* Now copy what we have collected and mapped */
elem = virtqueue_alloc_element(sz, out_num, in_num);
- elem->index = head;
+ elem->index = idx;
for (i = 0; i < out_num; i++) {
elem->out_sg[i] = iov[i];
}
@@ -1954,6 +1926,48 @@ vu_queue_pop(VuDev *dev, VuVirtq *vq, size_t sz)
elem->in_sg[i] = iov[out_num + i];
}
+ return elem;
+}
+
+void *
+vu_queue_pop(VuDev *dev, VuVirtq *vq, size_t sz)
+{
+ unsigned int head;
+ VuVirtqElement *elem;
+
+ if (unlikely(dev->broken) ||
+ unlikely(!vq->vring.avail)) {
+ return NULL;
+ }
+
+ if (vu_queue_empty(dev, vq)) {
+ return NULL;
+ }
+ /*
+ * Needed after virtio_queue_empty(), see comment in
+ * virtqueue_num_heads().
+ */
+ smp_rmb();
+
+ if (vq->inuse >= vq->vring.num) {
+ vu_panic(dev, "Virtqueue size exceeded");
+ return NULL;
+ }
+
+ if (!virtqueue_get_head(dev, vq, vq->last_avail_idx++, &head)) {
+ return NULL;
+ }
+
+ if (vu_has_feature(dev, VIRTIO_RING_F_EVENT_IDX)) {
+ vring_set_avail_event(vq, vq->last_avail_idx);
+ }
+
+ elem = vu_queue_map_desc(dev, vq, head, sz);
+
+ if (!elem) {
+ return NULL;
+ }
+
vq->inuse++;
return elem;
--
2.17.1
^ permalink raw reply related [flat|nested] 18+ messages in thread
* [Qemu-devel] [PATCH v6 4/7] libvhost-user: Support tracking inflight I/O in shared memory
2019-02-18 10:27 [Qemu-devel] [PATCH v6 0/7] vhost-user-blk: Add support for backend reconnecting elohimes
` (2 preceding siblings ...)
2019-02-18 10:27 ` [Qemu-devel] [PATCH v6 3/7] libvhost-user: Introduce vu_queue_map_desc() elohimes
@ 2019-02-18 10:27 ` elohimes
2019-02-18 10:27 ` [Qemu-devel] [PATCH v6 5/7] vhost-user-blk: Add support to get/set inflight buffer elohimes
` (3 subsequent siblings)
7 siblings, 0 replies; 18+ messages in thread
From: elohimes @ 2019-02-18 10:27 UTC (permalink / raw)
To: mst, stefanha, marcandre.lureau, berrange, jasowang,
maxime.coquelin, yury-kotov, wrfsh
Cc: qemu-devel, zhangyu31, chaiwen, nixun, lilin24, Xie Yongji
From: Xie Yongji <xieyongji@baidu.com>
This patch adds support for VHOST_USER_GET_INFLIGHT_FD and
VHOST_USER_SET_INFLIGHT_FD message to set/get shared buffer
to/from qemu. Then backend can track inflight I/O in this buffer.
Signed-off-by: Xie Yongji <xieyongji@baidu.com>
Signed-off-by: Zhang Yu <zhangyu31@baidu.com>
---
Makefile | 2 +-
contrib/libvhost-user/libvhost-user.c | 300 ++++++++++++++++++++++++--
contrib/libvhost-user/libvhost-user.h | 58 +++++
3 files changed, 339 insertions(+), 21 deletions(-)
diff --git a/Makefile b/Makefile
index 3658310b95..8469bd94fb 100644
--- a/Makefile
+++ b/Makefile
@@ -477,7 +477,7 @@ Makefile: $(version-obj-y)
# Build libraries
libqemuutil.a: $(util-obj-y) $(trace-obj-y) $(stub-obj-y)
-libvhost-user.a: $(libvhost-user-obj-y)
+libvhost-user.a: $(libvhost-user-obj-y) $(util-obj-y) $(stub-obj-y)
######################################################################
diff --git a/contrib/libvhost-user/libvhost-user.c b/contrib/libvhost-user/libvhost-user.c
index ea0f414b6d..c20850e890 100644
--- a/contrib/libvhost-user/libvhost-user.c
+++ b/contrib/libvhost-user/libvhost-user.c
@@ -41,6 +41,8 @@
#endif
#include "qemu/atomic.h"
+#include "qemu/osdep.h"
+#include "qemu/memfd.h"
#include "libvhost-user.h"
@@ -53,6 +55,18 @@
_min1 < _min2 ? _min1 : _min2; })
#endif
+/* Round number down to multiple */
+#define ALIGN_DOWN(n, m) ((n) / (m) * (m))
+
+/* Round number up to multiple */
+#define ALIGN_UP(n, m) ALIGN_DOWN((n) + (m) - 1, (m))
+
+/* Align each region to cache line size in inflight buffer */
+#define INFLIGHT_ALIGNMENT 64
+
+/* The version of inflight buffer */
+#define INFLIGHT_VERSION 1
+
#define VHOST_USER_HDR_SIZE offsetof(VhostUserMsg, payload.u64)
/* The version of the protocol we support */
@@ -66,6 +80,20 @@
} \
} while (0)
+static inline
+bool has_feature(uint64_t features, unsigned int fbit)
+{
+ assert(fbit < 64);
+ return !!(features & (1ULL << fbit));
+}
+
+static inline
+bool vu_has_feature(VuDev *dev,
+ unsigned int fbit)
+{
+ return has_feature(dev->features, fbit);
+}
+
static const char *
vu_request_to_string(unsigned int req)
{
@@ -100,6 +128,8 @@ vu_request_to_string(unsigned int req)
REQ(VHOST_USER_POSTCOPY_ADVISE),
REQ(VHOST_USER_POSTCOPY_LISTEN),
REQ(VHOST_USER_POSTCOPY_END),
+ REQ(VHOST_USER_GET_INFLIGHT_FD),
+ REQ(VHOST_USER_SET_INFLIGHT_FD),
REQ(VHOST_USER_MAX),
};
#undef REQ
@@ -890,6 +920,55 @@ vu_check_queue_msg_file(VuDev *dev, VhostUserMsg *vmsg)
return true;
}
+static int
+vu_check_queue_inflights(VuDev *dev, VuVirtq *vq)
+{
+ int i = 0;
+
+ if (!has_feature(dev->protocol_features,
+ VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD)) {
+ return 0;
+ }
+
+ if (unlikely(!vq->inflight)) {
+ return -1;
+ }
+
+ if (unlikely(!vq->inflight->version)) {
+ /* initialize the buffer */
+ vq->inflight->version = INFLIGHT_VERSION;
+ return 0;
+ }
+
+ vq->used_idx = vq->vring.used->idx;
+ vq->inflight_num = 0;
+
+ if (unlikely(vq->inflight->used_idx != vq->used_idx)) {
+ vq->inflight->desc[vq->inflight->process_head].inflight = 0;
+
+ barrier();
+
+ vq->inflight->used_idx = vq->used_idx;
+ }
+
+ for (i = 0; i < vq->inflight->desc_num; i++) {
+ if (vq->inflight->desc[i].inflight == 0) {
+ continue;
+ }
+
+ vq->inflight_desc[vq->inflight_num++] = i;
+ vq->inuse++;
+ }
+ vq->shadow_avail_idx = vq->last_avail_idx = vq->inuse + vq->used_idx;
+
+ /* in case of I/O hang after reconnecting */
+ if (eventfd_write(vq->kick_fd, 1)) {
+ return -1;
+ }
+
+ return 0;
+}
+
static bool
vu_set_vring_kick_exec(VuDev *dev, VhostUserMsg *vmsg)
{
@@ -923,6 +1002,10 @@ vu_set_vring_kick_exec(VuDev *dev, VhostUserMsg *vmsg)
dev->vq[index].kick_fd, index);
}
+ if (vu_check_queue_inflights(dev, &dev->vq[index])) {
+ vu_panic(dev, "Failed to check inflights for vq: %d\n", index);
+ }
+
return false;
}
@@ -995,6 +1078,11 @@ vu_set_vring_call_exec(VuDev *dev, VhostUserMsg *vmsg)
dev->vq[index].call_fd = vmsg->fds[0];
+ /* in case of I/O hang after reconnecting */
+ if (eventfd_write(vmsg->fds[0], 1)) {
+ return -1;
+ }
+
DPRINT("Got call_fd: %d for vq: %d\n", vmsg->fds[0], index);
return false;
@@ -1209,6 +1297,116 @@ vu_set_postcopy_end(VuDev *dev, VhostUserMsg *vmsg)
return true;
}
+static inline uint64_t
+vu_inflight_queue_size(uint16_t queue_size)
+{
+ return ALIGN_UP(sizeof(VuDescStateSplit) * queue_size +
+ sizeof(uint16_t), INFLIGHT_ALIGNMENT);
+}
+
+static bool
+vu_get_inflight_fd(VuDev *dev, VhostUserMsg *vmsg)
+{
+ int fd;
+ void *addr;
+ uint64_t mmap_size;
+ uint16_t num_queues, queue_size;
+
+ if (vmsg->size != sizeof(vmsg->payload.inflight)) {
+ vu_panic(dev, "Invalid get_inflight_fd message:%d", vmsg->size);
+ vmsg->payload.inflight.mmap_size = 0;
+ return true;
+ }
+
+ num_queues = vmsg->payload.inflight.num_queues;
+ queue_size = vmsg->payload.inflight.queue_size;
+
+ DPRINT("set_inflight_fd num_queues: %"PRId16"\n", num_queues);
+ DPRINT("set_inflight_fd queue_size: %"PRId16"\n", queue_size);
+
+ mmap_size = vu_inflight_queue_size(queue_size) * num_queues;
+
+ addr = qemu_memfd_alloc("vhost-inflight", mmap_size,
+ F_SEAL_GROW | F_SEAL_SHRINK | F_SEAL_SEAL,
+ &fd, NULL);
+
+ if (!addr) {
+ vu_panic(dev, "Failed to alloc vhost inflight area");
+ vmsg->payload.inflight.mmap_size = 0;
+ return true;
+ }
+
+ memset(addr, 0, mmap_size);
+
+ dev->inflight_info.addr = addr;
+ dev->inflight_info.size = vmsg->payload.inflight.mmap_size = mmap_size;
+ dev->inflight_info.fd = vmsg->fds[0] = fd;
+ vmsg->fd_num = 1;
+ vmsg->payload.inflight.mmap_offset = 0;
+
+ DPRINT("send inflight mmap_size: %"PRId64"\n",
+ vmsg->payload.inflight.mmap_size);
+ DPRINT("send inflight mmap offset: %"PRId64"\n",
+ vmsg->payload.inflight.mmap_offset);
+
+ return true;
+}
+
+static bool
+vu_set_inflight_fd(VuDev *dev, VhostUserMsg *vmsg)
+{
+ int fd, i;
+ uint64_t mmap_size, mmap_offset;
+ uint16_t num_queues, queue_size;
+ void *rc;
+
+ if (vmsg->fd_num != 1 ||
+ vmsg->size != sizeof(vmsg->payload.inflight)) {
+ vu_panic(dev, "Invalid set_inflight_fd message size:%d fds:%d",
+ vmsg->size, vmsg->fd_num);
+ return false;
+ }
+
+ fd = vmsg->fds[0];
+ mmap_size = vmsg->payload.inflight.mmap_size;
+ mmap_offset = vmsg->payload.inflight.mmap_offset;
+ num_queues = vmsg->payload.inflight.num_queues;
+ queue_size = vmsg->payload.inflight.queue_size;
+
+ DPRINT("set_inflight_fd mmap_size: %"PRId64"\n", mmap_size);
+ DPRINT("set_inflight_fd mmap_offset: %"PRId64"\n", mmap_offset);
+ DPRINT("set_inflight_fd num_queues: %"PRId16"\n", num_queues);
+ DPRINT("set_inflight_fd queue_size: %"PRId16"\n", queue_size);
+
+ rc = mmap(0, mmap_size, PROT_READ | PROT_WRITE, MAP_SHARED,
+ fd, mmap_offset);
+
+ if (rc == MAP_FAILED) {
+ vu_panic(dev, "set_inflight_fd mmap error: %s", strerror(errno));
+ return false;
+ }
+
+ if (dev->inflight_info.fd) {
+ close(dev->inflight_info.fd);
+ }
+
+ if (dev->inflight_info.addr) {
+ munmap(dev->inflight_info.addr, dev->inflight_info.size);
+ }
+
+ dev->inflight_info.fd = fd;
+ dev->inflight_info.addr = rc;
+ dev->inflight_info.size = mmap_size;
+
+ for (i = 0; i < num_queues; i++) {
+ dev->vq[i].inflight = (VuVirtqInflight *)rc;
+ dev->vq[i].inflight->desc_num = queue_size;
+ rc = (void *)((char *)rc + vu_inflight_queue_size(queue_size));
+ }
+
+ return false;
+}
+
static bool
vu_process_message(VuDev *dev, VhostUserMsg *vmsg)
{
@@ -1286,6 +1484,10 @@ vu_process_message(VuDev *dev, VhostUserMsg *vmsg)
return vu_set_postcopy_listen(dev, vmsg);
case VHOST_USER_POSTCOPY_END:
return vu_set_postcopy_end(dev, vmsg);
+ case VHOST_USER_GET_INFLIGHT_FD:
+ return vu_get_inflight_fd(dev, vmsg);
+ case VHOST_USER_SET_INFLIGHT_FD:
+ return vu_set_inflight_fd(dev, vmsg);
default:
vmsg_close_fds(vmsg);
vu_panic(dev, "Unhandled request: %d", vmsg->request);
@@ -1353,8 +1555,18 @@ vu_deinit(VuDev *dev)
close(vq->err_fd);
vq->err_fd = -1;
}
+ vq->inflight = NULL;
+ }
+
+ if (dev->inflight_info.addr) {
+ munmap(dev->inflight_info.addr, dev->inflight_info.size);
+ dev->inflight_info.addr = NULL;
}
+ if (dev->inflight_info.fd > 0) {
+ close(dev->inflight_info.fd);
+ dev->inflight_info.fd = -1;
+ }
vu_close_log(dev);
if (dev->slave_fd != -1) {
@@ -1681,20 +1893,6 @@ vu_queue_empty(VuDev *dev, VuVirtq *vq)
return vring_avail_idx(vq) == vq->last_avail_idx;
}
-static inline
-bool has_feature(uint64_t features, unsigned int fbit)
-{
- assert(fbit < 64);
- return !!(features & (1ULL << fbit));
-}
-
-static inline
-bool vu_has_feature(VuDev *dev,
- unsigned int fbit)
-{
- return has_feature(dev->features, fbit);
-}
-
static bool
vring_notify(VuDev *dev, VuVirtq *vq)
{
@@ -1823,12 +2021,6 @@ virtqueue_map_desc(VuDev *dev,
*p_num_sg = num_sg;
}
-/* Round number down to multiple */
-#define ALIGN_DOWN(n, m) ((n) / (m) * (m))
-
-/* Round number up to multiple */
-#define ALIGN_UP(n, m) ALIGN_DOWN((n) + (m) - 1, (m))
-
static void *
virtqueue_alloc_element(size_t sz,
unsigned out_num, unsigned in_num)
@@ -1929,9 +2121,67 @@ vu_queue_map_desc(VuDev *dev, VuVirtq *vq, unsigned int idx, size_t sz)
return elem;
}
+static int
+vu_queue_inflight_get(VuDev *dev, VuVirtq *vq, int desc_idx)
+{
+ if (!has_feature(dev->protocol_features,
+ VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD)) {
+ return 0;
+ }
+
+ if (unlikely(!vq->inflight)) {
+ return -1;
+ }
+
+ vq->inflight->desc[desc_idx].inflight = 1;
+
+ return 0;
+}
+
+static int
+vu_queue_inflight_pre_put(VuDev *dev, VuVirtq *vq, int desc_idx)
+{
+ if (!has_feature(dev->protocol_features,
+ VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD)) {
+ return 0;
+ }
+
+ if (unlikely(!vq->inflight)) {
+ return -1;
+ }
+
+ vq->inflight->process_head = desc_idx;
+
+ return 0;
+}
+
+static int
+vu_queue_inflight_post_put(VuDev *dev, VuVirtq *vq, int desc_idx)
+{
+ if (!has_feature(dev->protocol_features,
+ VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD)) {
+ return 0;
+ }
+
+ if (unlikely(!vq->inflight)) {
+ return -1;
+ }
+
+ barrier();
+
+ vq->inflight->desc[desc_idx].inflight = 0;
+
+ barrier();
+
+ vq->inflight->used_idx = vq->used_idx;
+
+ return 0;
+}
+
void *
vu_queue_pop(VuDev *dev, VuVirtq *vq, size_t sz)
{
+ int i;
unsigned int head;
VuVirtqElement *elem;
@@ -1940,6 +2190,12 @@ vu_queue_pop(VuDev *dev, VuVirtq *vq, size_t sz)
return NULL;
}
+ if (unlikely(vq->inflight_num > 0)) {
+ i = (--vq->inflight_num);
+ elem = vu_queue_map_desc(dev, vq, vq->inflight_desc[i], sz);
+ return elem;
+ }
+
if (vu_queue_empty(dev, vq)) {
return NULL;
}
@@ -1970,6 +2226,8 @@ vu_queue_pop(VuDev *dev, VuVirtq *vq, size_t sz)
vq->inuse++;
+ vu_queue_inflight_get(dev, vq, head);
+
return elem;
}
@@ -2114,5 +2372,7 @@ vu_queue_push(VuDev *dev, VuVirtq *vq,
const VuVirtqElement *elem, unsigned int len)
{
vu_queue_fill(dev, vq, elem, len, 0);
+ vu_queue_inflight_pre_put(dev, vq, elem->index);
vu_queue_flush(dev, vq, 1);
+ vu_queue_inflight_post_put(dev, vq, elem->index);
}
diff --git a/contrib/libvhost-user/libvhost-user.h b/contrib/libvhost-user/libvhost-user.h
index 4aa55b4d2d..b1ca7fc5c1 100644
--- a/contrib/libvhost-user/libvhost-user.h
+++ b/contrib/libvhost-user/libvhost-user.h
@@ -53,6 +53,7 @@ enum VhostUserProtocolFeature {
VHOST_USER_PROTOCOL_F_CONFIG = 9,
VHOST_USER_PROTOCOL_F_SLAVE_SEND_FD = 10,
VHOST_USER_PROTOCOL_F_HOST_NOTIFIER = 11,
+ VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD = 12,
VHOST_USER_PROTOCOL_F_MAX
};
@@ -91,6 +92,8 @@ typedef enum VhostUserRequest {
VHOST_USER_POSTCOPY_ADVISE = 28,
VHOST_USER_POSTCOPY_LISTEN = 29,
VHOST_USER_POSTCOPY_END = 30,
+ VHOST_USER_GET_INFLIGHT_FD = 31,
+ VHOST_USER_SET_INFLIGHT_FD = 32,
VHOST_USER_MAX
} VhostUserRequest;
@@ -138,6 +141,13 @@ typedef struct VhostUserVringArea {
uint64_t offset;
} VhostUserVringArea;
+typedef struct VhostUserInflight {
+ uint64_t mmap_size;
+ uint64_t mmap_offset;
+ uint16_t num_queues;
+ uint16_t queue_size;
+} VhostUserInflight;
+
#if defined(_WIN32)
# define VU_PACKED __attribute__((gcc_struct, packed))
#else
@@ -163,6 +173,7 @@ typedef struct VhostUserMsg {
VhostUserLog log;
VhostUserConfig config;
VhostUserVringArea area;
+ VhostUserInflight inflight;
} payload;
int fds[VHOST_MEMORY_MAX_NREGIONS];
@@ -234,9 +245,49 @@ typedef struct VuRing {
uint32_t flags;
} VuRing;
+typedef struct VuDescStateSplit {
+ /* Indicate whether this descriptor is inflight or not.
+ * Only available for head-descriptor. */
+ uint8_t inflight;
+
+ /* Padding */
+ uint8_t padding;
+
+ /* Link to the last processed entry */
+ uint16_t next;
+} VuDescStateSplit;
+
+typedef struct VuVirtqInflight {
+ /* The feature flags of this region. Now it's initialized to 0. */
+ uint64_t features;
+
+ /* The version of this region. It's 1 currently.
+ * Zero value indicates a vm reset happened. */
+ uint16_t version;
+
+ /* The size of VuDescStateSplit array. It's equal to the virtqueue
+ * size. Slave could get it from queue size field of VhostUserInflight. */
+ uint16_t desc_num;
+
+ /* The head of processed VuDescStateSplit entry list */
+ uint16_t process_head;
+
+ /* Storing the idx value of used ring */
+ uint16_t used_idx;
+
+ /* Used to track the state of each descriptor in descriptor table */
+ VuDescStateSplit desc[0];
+} VuVirtqInflight;
+
typedef struct VuVirtq {
VuRing vring;
+ VuVirtqInflight *inflight;
+
+ uint16_t inflight_desc[VIRTQUEUE_MAX_SIZE];
+
+ uint16_t inflight_num;
+
/* Next head to pop */
uint16_t last_avail_idx;
@@ -279,11 +330,18 @@ typedef void (*vu_set_watch_cb) (VuDev *dev, int fd, int condition,
vu_watch_cb cb, void *data);
typedef void (*vu_remove_watch_cb) (VuDev *dev, int fd);
+typedef struct VuDevInflightInfo {
+ int fd;
+ void *addr;
+ uint64_t size;
+} VuDevInflightInfo;
+
struct VuDev {
int sock;
uint32_t nregions;
VuDevRegion regions[VHOST_MEMORY_MAX_NREGIONS];
VuVirtq vq[VHOST_MAX_NR_VIRTQUEUE];
+ VuDevInflightInfo inflight_info;
int log_call_fd;
int slave_fd;
uint64_t log_size;
--
2.17.1
^ permalink raw reply related [flat|nested] 18+ messages in thread
* [Qemu-devel] [PATCH v6 5/7] vhost-user-blk: Add support to get/set inflight buffer
2019-02-18 10:27 [Qemu-devel] [PATCH v6 0/7] vhost-user-blk: Add support for backend reconnecting elohimes
` (3 preceding siblings ...)
2019-02-18 10:27 ` [Qemu-devel] [PATCH v6 4/7] libvhost-user: Support tracking inflight I/O in shared memory elohimes
@ 2019-02-18 10:27 ` elohimes
2019-02-18 10:27 ` [Qemu-devel] [PATCH v6 6/7] vhost-user-blk: Add support to reconnect backend elohimes
` (2 subsequent siblings)
7 siblings, 0 replies; 18+ messages in thread
From: elohimes @ 2019-02-18 10:27 UTC (permalink / raw)
To: mst, stefanha, marcandre.lureau, berrange, jasowang,
maxime.coquelin, yury-kotov, wrfsh
Cc: qemu-devel, zhangyu31, chaiwen, nixun, lilin24, Xie Yongji
From: Xie Yongji <xieyongji@baidu.com>
This patch adds support for vhost-user-blk device to get/set
inflight buffer from/to backend.
Signed-off-by: Xie Yongji <xieyongji@baidu.com>
Signed-off-by: Zhang Yu <zhangyu31@baidu.com>
---
hw/block/vhost-user-blk.c | 28 ++++++++++++++++++++++++++++
include/hw/virtio/vhost-user-blk.h | 1 +
2 files changed, 29 insertions(+)
diff --git a/hw/block/vhost-user-blk.c b/hw/block/vhost-user-blk.c
index 44ac814016..9682df1a7b 100644
--- a/hw/block/vhost-user-blk.c
+++ b/hw/block/vhost-user-blk.c
@@ -128,6 +128,21 @@ static void vhost_user_blk_start(VirtIODevice *vdev)
}
s->dev.acked_features = vdev->guest_features;
+
+ if (!s->inflight->addr) {
+ ret = vhost_dev_get_inflight(&s->dev, s->queue_size, s->inflight);
+ if (ret < 0) {
+ error_report("Error get inflight: %d", -ret);
+ goto err_guest_notifiers;
+ }
+ }
+
+ ret = vhost_dev_set_inflight(&s->dev, s->inflight);
+ if (ret < 0) {
+ error_report("Error set inflight: %d", -ret);
+ goto err_guest_notifiers;
+ }
+
ret = vhost_dev_start(&s->dev, vdev);
if (ret < 0) {
error_report("Error starting vhost: %d", -ret);
@@ -249,6 +264,13 @@ static void vhost_user_blk_handle_output(VirtIODevice *vdev, VirtQueue *vq)
}
}
+static void vhost_user_blk_reset(VirtIODevice *vdev)
+{
+ VHostUserBlk *s = VHOST_USER_BLK(vdev);
+
+ vhost_dev_free_inflight(s->inflight);
+}
+
static void vhost_user_blk_device_realize(DeviceState *dev, Error **errp)
{
VirtIODevice *vdev = VIRTIO_DEVICE(dev);
@@ -289,6 +311,8 @@ static void vhost_user_blk_device_realize(DeviceState *dev, Error **errp)
vhost_user_blk_handle_output);
}
+ s->inflight = g_new0(struct vhost_inflight, 1);
+
s->dev.nvqs = s->num_queues;
s->dev.vqs = g_new(struct vhost_virtqueue, s->dev.nvqs);
s->dev.vq_index = 0;
@@ -321,6 +345,7 @@ vhost_err:
vhost_dev_cleanup(&s->dev);
virtio_err:
g_free(vqs);
+ g_free(s->inflight);
virtio_cleanup(vdev);
vhost_user_cleanup(user);
@@ -336,7 +361,9 @@ static void vhost_user_blk_device_unrealize(DeviceState *dev, Error **errp)
vhost_user_blk_set_status(vdev, 0);
vhost_dev_cleanup(&s->dev);
+ vhost_dev_free_inflight(s->inflight);
g_free(vqs);
+ g_free(s->inflight);
virtio_cleanup(vdev);
if (s->vhost_user) {
@@ -386,6 +413,7 @@ static void vhost_user_blk_class_init(ObjectClass *klass, void *data)
vdc->set_config = vhost_user_blk_set_config;
vdc->get_features = vhost_user_blk_get_features;
vdc->set_status = vhost_user_blk_set_status;
+ vdc->reset = vhost_user_blk_reset;
}
static const TypeInfo vhost_user_blk_info = {
diff --git a/include/hw/virtio/vhost-user-blk.h b/include/hw/virtio/vhost-user-blk.h
index d52944aeeb..445516604a 100644
--- a/include/hw/virtio/vhost-user-blk.h
+++ b/include/hw/virtio/vhost-user-blk.h
@@ -36,6 +36,7 @@ typedef struct VHostUserBlk {
uint32_t queue_size;
uint32_t config_wce;
struct vhost_dev dev;
+ struct vhost_inflight *inflight;
VhostUserState *vhost_user;
} VHostUserBlk;
--
2.17.1
^ permalink raw reply related [flat|nested] 18+ messages in thread
* [Qemu-devel] [PATCH v6 6/7] vhost-user-blk: Add support to reconnect backend
2019-02-18 10:27 [Qemu-devel] [PATCH v6 0/7] vhost-user-blk: Add support for backend reconnecting elohimes
` (4 preceding siblings ...)
2019-02-18 10:27 ` [Qemu-devel] [PATCH v6 5/7] vhost-user-blk: Add support to get/set inflight buffer elohimes
@ 2019-02-18 10:27 ` elohimes
2019-02-18 10:27 ` [Qemu-devel] [PATCH v6 7/7] contrib/vhost-user-blk: enable inflight I/O tracking elohimes
2019-02-20 19:59 ` [Qemu-devel] [PATCH v6 0/7] vhost-user-blk: Add support for backend reconnecting Michael S. Tsirkin
7 siblings, 0 replies; 18+ messages in thread
From: elohimes @ 2019-02-18 10:27 UTC (permalink / raw)
To: mst, stefanha, marcandre.lureau, berrange, jasowang,
maxime.coquelin, yury-kotov, wrfsh
Cc: qemu-devel, zhangyu31, chaiwen, nixun, lilin24, Xie Yongji
From: Xie Yongji <xieyongji@baidu.com>
Since we now support the message VHOST_USER_GET_INFLIGHT_FD
and VHOST_USER_SET_INFLIGHT_FD. The backend is able to restart
safely because it can track inflight I/O in shared memory.
This patch allows qemu to reconnect the backend after
connection closed.
Signed-off-by: Xie Yongji <xieyongji@baidu.com>
Signed-off-by: Ni Xun <nixun@baidu.com>
Signed-off-by: Zhang Yu <zhangyu31@baidu.com>
---
hw/block/vhost-user-blk.c | 205 +++++++++++++++++++++++------
include/hw/virtio/vhost-user-blk.h | 4 +
2 files changed, 167 insertions(+), 42 deletions(-)
diff --git a/hw/block/vhost-user-blk.c b/hw/block/vhost-user-blk.c
index 9682df1a7b..539ea2e571 100644
--- a/hw/block/vhost-user-blk.c
+++ b/hw/block/vhost-user-blk.c
@@ -103,7 +103,7 @@ const VhostDevConfigOps blk_ops = {
.vhost_dev_config_notifier = vhost_user_blk_handle_config_change,
};
-static void vhost_user_blk_start(VirtIODevice *vdev)
+static int vhost_user_blk_start(VirtIODevice *vdev)
{
VHostUserBlk *s = VHOST_USER_BLK(vdev);
BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(vdev)));
@@ -112,13 +112,13 @@ static void vhost_user_blk_start(VirtIODevice *vdev)
if (!k->set_guest_notifiers) {
error_report("binding does not support guest notifiers");
- return;
+ return -ENOSYS;
}
ret = vhost_dev_enable_notifiers(&s->dev, vdev);
if (ret < 0) {
error_report("Error enabling host notifiers: %d", -ret);
- return;
+ return ret;
}
ret = k->set_guest_notifiers(qbus->parent, s->dev.nvqs, true);
@@ -157,12 +157,13 @@ static void vhost_user_blk_start(VirtIODevice *vdev)
vhost_virtqueue_mask(&s->dev, vdev, i, false);
}
- return;
+ return ret;
err_guest_notifiers:
k->set_guest_notifiers(qbus->parent, s->dev.nvqs, false);
err_host_notifiers:
vhost_dev_disable_notifiers(&s->dev, vdev);
+ return ret;
}
static void vhost_user_blk_stop(VirtIODevice *vdev)
@@ -181,7 +182,6 @@ static void vhost_user_blk_stop(VirtIODevice *vdev)
ret = k->set_guest_notifiers(qbus->parent, s->dev.nvqs, false);
if (ret < 0) {
error_report("vhost guest notifier cleanup failed: %d", ret);
- return;
}
vhost_dev_disable_notifiers(&s->dev, vdev);
@@ -191,21 +191,43 @@ static void vhost_user_blk_set_status(VirtIODevice *vdev, uint8_t status)
{
VHostUserBlk *s = VHOST_USER_BLK(vdev);
bool should_start = status & VIRTIO_CONFIG_S_DRIVER_OK;
+ int ret;
if (!vdev->vm_running) {
should_start = false;
}
- if (s->dev.started == should_start) {
+ if (s->should_start == should_start) {
+ return;
+ }
+
+ if (!s->connected || s->dev.started == should_start) {
+ s->should_start = should_start;
return;
}
if (should_start) {
- vhost_user_blk_start(vdev);
+ s->should_start = true;
+ /*
+ * make sure vhost_user_blk_handle_output() ignores fake
+ * guest kick by vhost_dev_enable_notifiers()
+ */
+ barrier();
+ ret = vhost_user_blk_start(vdev);
+ if (ret < 0) {
+ error_report("vhost-user-blk: vhost start failed: %s",
+ strerror(-ret));
+ qemu_chr_fe_disconnect(&s->chardev);
+ }
} else {
vhost_user_blk_stop(vdev);
+ /*
+ * make sure vhost_user_blk_handle_output() ignore fake
+ * guest kick by vhost_dev_disable_notifiers()
+ */
+ barrier();
+ s->should_start = false;
}
-
}
static uint64_t vhost_user_blk_get_features(VirtIODevice *vdev,
@@ -237,13 +259,22 @@ static uint64_t vhost_user_blk_get_features(VirtIODevice *vdev,
static void vhost_user_blk_handle_output(VirtIODevice *vdev, VirtQueue *vq)
{
VHostUserBlk *s = VHOST_USER_BLK(vdev);
- int i;
+ int i, ret;
if (!(virtio_host_has_feature(vdev, VIRTIO_F_VERSION_1) &&
!virtio_vdev_has_feature(vdev, VIRTIO_F_VERSION_1))) {
return;
}
+ if (s->should_start) {
+ return;
+ }
+ s->should_start = true;
+
+ if (!s->connected) {
+ return;
+ }
+
if (s->dev.started) {
return;
}
@@ -251,7 +282,13 @@ static void vhost_user_blk_handle_output(VirtIODevice *vdev, VirtQueue *vq)
/* Some guests kick before setting VIRTIO_CONFIG_S_DRIVER_OK so start
* vhost here instead of waiting for .set_status().
*/
- vhost_user_blk_start(vdev);
+ ret = vhost_user_blk_start(vdev);
+ if (ret < 0) {
+ error_report("vhost-user-blk: vhost start failed: %s",
+ strerror(-ret));
+ qemu_chr_fe_disconnect(&s->chardev);
+ return;
+ }
/* Kick right away to begin processing requests already in vring */
for (i = 0; i < s->dev.nvqs; i++) {
@@ -271,13 +308,106 @@ static void vhost_user_blk_reset(VirtIODevice *vdev)
vhost_dev_free_inflight(s->inflight);
}
+static int vhost_user_blk_connect(DeviceState *dev)
+{
+ VirtIODevice *vdev = VIRTIO_DEVICE(dev);
+ VHostUserBlk *s = VHOST_USER_BLK(vdev);
+ int ret = 0;
+
+ if (s->connected) {
+ return 0;
+ }
+ s->connected = true;
+
+ s->dev.nvqs = s->num_queues;
+ s->dev.vqs = s->vqs;
+ s->dev.vq_index = 0;
+ s->dev.backend_features = 0;
+
+ vhost_dev_set_config_notifier(&s->dev, &blk_ops);
+
+ ret = vhost_dev_init(&s->dev, s->vhost_user, VHOST_BACKEND_TYPE_USER, 0);
+ if (ret < 0) {
+ error_report("vhost-user-blk: vhost initialization failed: %s",
+ strerror(-ret));
+ return ret;
+ }
+
+ /* restore vhost state */
+ if (s->should_start) {
+ ret = vhost_user_blk_start(vdev);
+ if (ret < 0) {
+ error_report("vhost-user-blk: vhost start failed: %s",
+ strerror(-ret));
+ return ret;
+ }
+ }
+
+ return 0;
+}
+
+static void vhost_user_blk_disconnect(DeviceState *dev)
+{
+ VirtIODevice *vdev = VIRTIO_DEVICE(dev);
+ VHostUserBlk *s = VHOST_USER_BLK(vdev);
+
+ if (!s->connected) {
+ return;
+ }
+ s->connected = false;
+
+ if (s->dev.started) {
+ vhost_user_blk_stop(vdev);
+ }
+
+ vhost_dev_cleanup(&s->dev);
+}
+
+static gboolean vhost_user_blk_watch(GIOChannel *chan, GIOCondition cond,
+ void *opaque)
+{
+ DeviceState *dev = opaque;
+ VirtIODevice *vdev = VIRTIO_DEVICE(dev);
+ VHostUserBlk *s = VHOST_USER_BLK(vdev);
+
+ qemu_chr_fe_disconnect(&s->chardev);
+
+ return true;
+}
+
+static void vhost_user_blk_event(void *opaque, int event)
+{
+ DeviceState *dev = opaque;
+ VirtIODevice *vdev = VIRTIO_DEVICE(dev);
+ VHostUserBlk *s = VHOST_USER_BLK(vdev);
+
+ switch (event) {
+ case CHR_EVENT_OPENED:
+ if (vhost_user_blk_connect(dev) < 0) {
+ qemu_chr_fe_disconnect(&s->chardev);
+ return;
+ }
+ s->watch = qemu_chr_fe_add_watch(&s->chardev, G_IO_HUP,
+ vhost_user_blk_watch, dev);
+ break;
+ case CHR_EVENT_CLOSED:
+ vhost_user_blk_disconnect(dev);
+ if (s->watch) {
+ g_source_remove(s->watch);
+ s->watch = 0;
+ }
+ break;
+ }
+}
+
+
static void vhost_user_blk_device_realize(DeviceState *dev, Error **errp)
{
VirtIODevice *vdev = VIRTIO_DEVICE(dev);
VHostUserBlk *s = VHOST_USER_BLK(vdev);
VhostUserState *user;
- struct vhost_virtqueue *vqs = NULL;
int i, ret;
+ Error *err = NULL;
if (!s->chardev.chr) {
error_setg(errp, "vhost-user-blk: chardev is mandatory");
@@ -312,27 +442,28 @@ static void vhost_user_blk_device_realize(DeviceState *dev, Error **errp)
}
s->inflight = g_new0(struct vhost_inflight, 1);
-
- s->dev.nvqs = s->num_queues;
- s->dev.vqs = g_new(struct vhost_virtqueue, s->dev.nvqs);
- s->dev.vq_index = 0;
- s->dev.backend_features = 0;
- vqs = s->dev.vqs;
-
- vhost_dev_set_config_notifier(&s->dev, &blk_ops);
-
- ret = vhost_dev_init(&s->dev, s->vhost_user, VHOST_BACKEND_TYPE_USER, 0);
- if (ret < 0) {
- error_setg(errp, "vhost-user-blk: vhost initialization failed: %s",
- strerror(-ret));
- goto virtio_err;
- }
+ s->vqs = g_new(struct vhost_virtqueue, s->num_queues);
+ s->watch = 0;
+ s->should_start = false;
+ s->connected = false;
+
+ qemu_chr_fe_set_handlers(&s->chardev, NULL, NULL, vhost_user_blk_event,
+ NULL, (void *)dev, NULL, true);
+
+reconnect:
+ do {
+ if (qemu_chr_fe_wait_connected(&s->chardev, &err) < 0) {
+ error_report_err(err);
+ err = NULL;
+ sleep(1);
+ }
+ } while (!s->connected);
ret = vhost_dev_get_config(&s->dev, (uint8_t *)&s->blkcfg,
- sizeof(struct virtio_blk_config));
+ sizeof(struct virtio_blk_config));
if (ret < 0) {
- error_setg(errp, "vhost-user-blk: get block config failed");
- goto vhost_err;
+ error_report("vhost-user-blk: get block config failed");
+ goto reconnect;
}
if (s->blkcfg.num_queues != s->num_queues) {
@@ -340,29 +471,19 @@ static void vhost_user_blk_device_realize(DeviceState *dev, Error **errp)
}
return;
-
-vhost_err:
- vhost_dev_cleanup(&s->dev);
-virtio_err:
- g_free(vqs);
- g_free(s->inflight);
- virtio_cleanup(vdev);
-
- vhost_user_cleanup(user);
- g_free(user);
- s->vhost_user = NULL;
}
static void vhost_user_blk_device_unrealize(DeviceState *dev, Error **errp)
{
VirtIODevice *vdev = VIRTIO_DEVICE(dev);
VHostUserBlk *s = VHOST_USER_BLK(dev);
- struct vhost_virtqueue *vqs = s->dev.vqs;
vhost_user_blk_set_status(vdev, 0);
+ qemu_chr_fe_set_handlers(&s->chardev, NULL, NULL, NULL,
+ NULL, NULL, NULL, false);
vhost_dev_cleanup(&s->dev);
vhost_dev_free_inflight(s->inflight);
- g_free(vqs);
+ g_free(s->vqs);
g_free(s->inflight);
virtio_cleanup(vdev);
diff --git a/include/hw/virtio/vhost-user-blk.h b/include/hw/virtio/vhost-user-blk.h
index 445516604a..4849aa5eb5 100644
--- a/include/hw/virtio/vhost-user-blk.h
+++ b/include/hw/virtio/vhost-user-blk.h
@@ -38,6 +38,10 @@ typedef struct VHostUserBlk {
struct vhost_dev dev;
struct vhost_inflight *inflight;
VhostUserState *vhost_user;
+ struct vhost_virtqueue *vqs;
+ guint watch;
+ bool should_start;
+ bool connected;
} VHostUserBlk;
#endif
--
2.17.1
^ permalink raw reply related [flat|nested] 18+ messages in thread
* [Qemu-devel] [PATCH v6 7/7] contrib/vhost-user-blk: enable inflight I/O tracking
2019-02-18 10:27 [Qemu-devel] [PATCH v6 0/7] vhost-user-blk: Add support for backend reconnecting elohimes
` (5 preceding siblings ...)
2019-02-18 10:27 ` [Qemu-devel] [PATCH v6 6/7] vhost-user-blk: Add support to reconnect backend elohimes
@ 2019-02-18 10:27 ` elohimes
2019-02-20 19:59 ` [Qemu-devel] [PATCH v6 0/7] vhost-user-blk: Add support for backend reconnecting Michael S. Tsirkin
7 siblings, 0 replies; 18+ messages in thread
From: elohimes @ 2019-02-18 10:27 UTC (permalink / raw)
To: mst, stefanha, marcandre.lureau, berrange, jasowang,
maxime.coquelin, yury-kotov, wrfsh
Cc: qemu-devel, zhangyu31, chaiwen, nixun, lilin24, Xie Yongji
From: Xie Yongji <xieyongji@baidu.com>
This patch enables inflight I/O tracking for
vhost-user-blk backend so that we could restart it safely.
Signed-off-by: Xie Yongji <xieyongji@baidu.com>
Signed-off-by: Zhang Yu <zhangyu31@baidu.com>
---
contrib/vhost-user-blk/vhost-user-blk.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/contrib/vhost-user-blk/vhost-user-blk.c b/contrib/vhost-user-blk/vhost-user-blk.c
index 43583f2659..86a3987744 100644
--- a/contrib/vhost-user-blk/vhost-user-blk.c
+++ b/contrib/vhost-user-blk/vhost-user-blk.c
@@ -398,7 +398,8 @@ vub_get_features(VuDev *dev)
static uint64_t
vub_get_protocol_features(VuDev *dev)
{
- return 1ull << VHOST_USER_PROTOCOL_F_CONFIG;
+ return 1ull << VHOST_USER_PROTOCOL_F_CONFIG |
+ 1ull << VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD;
}
static int
--
2.17.1
^ permalink raw reply related [flat|nested] 18+ messages in thread
* Re: [Qemu-devel] [PATCH v6 0/7] vhost-user-blk: Add support for backend reconnecting
2019-02-18 10:27 [Qemu-devel] [PATCH v6 0/7] vhost-user-blk: Add support for backend reconnecting elohimes
` (6 preceding siblings ...)
2019-02-18 10:27 ` [Qemu-devel] [PATCH v6 7/7] contrib/vhost-user-blk: enable inflight I/O tracking elohimes
@ 2019-02-20 19:59 ` Michael S. Tsirkin
2019-02-21 1:30 ` Yongji Xie
7 siblings, 1 reply; 18+ messages in thread
From: Michael S. Tsirkin @ 2019-02-20 19:59 UTC (permalink / raw)
To: elohimes
Cc: stefanha, marcandre.lureau, berrange, jasowang, maxime.coquelin,
yury-kotov, wrfsh, qemu-devel, zhangyu31, chaiwen, nixun,
lilin24, Xie Yongji
On Mon, Feb 18, 2019 at 06:27:41PM +0800, elohimes@gmail.com wrote:
> From: Xie Yongji <xieyongji@baidu.com>
>
> This patchset is aimed at supporting qemu to reconnect
> vhost-user-blk backend after vhost-user-blk backend crash or
> restart.
>
> The patch 1 introduces two new messages VHOST_USER_GET_INFLIGHT_FD
> and VHOST_USER_SET_INFLIGHT_FD to support transferring shared
> buffer between qemu and backend.
>
> The patch 2 deletes some redundant check in contrib/libvhost-user.c.
>
> The patch 3,4 are the corresponding libvhost-user patches of
> patch 1. Make libvhost-user support VHOST_USER_GET_INFLIGHT_FD
> and VHOST_USER_SET_INFLIGHT_FD.
>
> The patch 5 allows vhost-user-blk to use the two new messages
> to get/set inflight buffer from/to backend.
>
> The patch 6 supports vhost-user-blk to reconnect backend when
> connection closed.
>
> The patch 7 introduces VHOST_USER_PROTOCOL_F_SLAVE_SHMFD
> to vhost-user-blk backend which is used to tell qemu that
> we support reconnecting now.
>
> To use it, we could start qemu with:
>
> qemu-system-x86_64 \
> -chardev socket,id=char0,path=/path/vhost.socket,reconnect=1, \
> -device vhost-user-blk-pci,chardev=char0 \
>
> and start vhost-user-blk backend with:
>
> vhost-user-blk -b /path/file -s /path/vhost.socket
>
> Then we can restart vhost-user-blk at any time during VM running.
Sorry is elohimes@gmail.com also an address that belongs to
Xie Yongji?
If not we need a signed off by from that address'
owner as well.
Thanks!
> V5 to V6:
> - Document the layout in inflight buffer for packed virtqueue
> - Rework the layout in inflight buffer for split virtqueue
> - Remove version field in VhostUserInflight
> - Add a patch to remove some redundant check in
> contrib/libvhost-user.c
> - Document more details in vhost-user.txt
>
> V4 to V5:
> - Drop patch that enables "nowait" option on client sockets
> - Support resubmitting inflight I/O in order
> - Make inflight I/O tracking more robust
> - Remove align field and add queue size field in VhostUserInflight
> - Document more details in vhost-user.txt
>
> V3 to V4:
> - Drop messages VHOST_USER_GET_SHM_SIZE and VHOST_USER_SET_SHM_FD
> - Introduce two new messages VHOST_USER_GET_INFLIGHT_FD
> and VHOST_USER_SET_INFLIGHT_FD
> - Allocate inflight buffer in backend rather than in qemu
> - Document a recommended format for inflight buffer
>
> V2 to V3:
> - Using exisiting wait/nowait options to control connection on
> client sockets instead of introducing "disconnected" option.
> - Support the case that vhost-user backend restart during initialzation
> of vhost-user-blk device.
>
> V1 to V2:
> - Introduce "disconnected" option for chardev instead of reuse "wait"
> option
> - Support the case that QEMU starts before vhost-user backend
> - Drop message VHOST_USER_SET_VRING_INFLIGHT
> - Introduce two new messages VHOST_USER_GET_SHM_SIZE
> and VHOST_USER_SET_SHM_FD
>
> Xie Yongji (7):
> vhost-user: Support transferring inflight buffer between qemu and
> backend
> libvhost-user: Remove unnecessary FD flag check for event file
> descriptors
> libvhost-user: Introduce vu_queue_map_desc()
> libvhost-user: Support tracking inflight I/O in shared memory
> vhost-user-blk: Add support to get/set inflight buffer
> vhost-user-blk: Add support to reconnect backend
> contrib/vhost-user-blk: enable inflight I/O tracking
>
> Makefile | 2 +-
> contrib/libvhost-user/libvhost-user.c | 400 ++++++++++++++++++++----
> contrib/libvhost-user/libvhost-user.h | 58 ++++
> contrib/vhost-user-blk/vhost-user-blk.c | 3 +-
> docs/interop/vhost-user.txt | 264 ++++++++++++++++
> hw/block/vhost-user-blk.c | 229 +++++++++++---
> hw/virtio/vhost-user.c | 107 +++++++
> hw/virtio/vhost.c | 96 ++++++
> include/hw/virtio/vhost-backend.h | 10 +
> include/hw/virtio/vhost-user-blk.h | 5 +
> include/hw/virtio/vhost.h | 18 ++
> 11 files changed, 1084 insertions(+), 108 deletions(-)
>
> --
> 2.17.1
^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [Qemu-devel] [PATCH v6 0/7] vhost-user-blk: Add support for backend reconnecting
2019-02-20 19:59 ` [Qemu-devel] [PATCH v6 0/7] vhost-user-blk: Add support for backend reconnecting Michael S. Tsirkin
@ 2019-02-21 1:30 ` Yongji Xie
0 siblings, 0 replies; 18+ messages in thread
From: Yongji Xie @ 2019-02-21 1:30 UTC (permalink / raw)
To: Michael S. Tsirkin
Cc: Stefan Hajnoczi, Marc-André Lureau, Daniel P. Berrangé,
Jason Wang, Coquelin, Maxime, Yury Kotov,
Евгений
Яковлев,
qemu-devel, zhangyu31, chaiwen, nixun, lilin24, Xie Yongji
On Thu, 21 Feb 2019 at 04:00, Michael S. Tsirkin <mst@redhat.com> wrote:
>
> On Mon, Feb 18, 2019 at 06:27:41PM +0800, elohimes@gmail.com wrote:
> > From: Xie Yongji <xieyongji@baidu.com>
> >
> > This patchset is aimed at supporting qemu to reconnect
> > vhost-user-blk backend after vhost-user-blk backend crash or
> > restart.
> >
> > The patch 1 introduces two new messages VHOST_USER_GET_INFLIGHT_FD
> > and VHOST_USER_SET_INFLIGHT_FD to support transferring shared
> > buffer between qemu and backend.
> >
> > The patch 2 deletes some redundant check in contrib/libvhost-user.c.
> >
> > The patch 3,4 are the corresponding libvhost-user patches of
> > patch 1. Make libvhost-user support VHOST_USER_GET_INFLIGHT_FD
> > and VHOST_USER_SET_INFLIGHT_FD.
> >
> > The patch 5 allows vhost-user-blk to use the two new messages
> > to get/set inflight buffer from/to backend.
> >
> > The patch 6 supports vhost-user-blk to reconnect backend when
> > connection closed.
> >
> > The patch 7 introduces VHOST_USER_PROTOCOL_F_SLAVE_SHMFD
> > to vhost-user-blk backend which is used to tell qemu that
> > we support reconnecting now.
> >
> > To use it, we could start qemu with:
> >
> > qemu-system-x86_64 \
> > -chardev socket,id=char0,path=/path/vhost.socket,reconnect=1, \
> > -device vhost-user-blk-pci,chardev=char0 \
> >
> > and start vhost-user-blk backend with:
> >
> > vhost-user-blk -b /path/file -s /path/vhost.socket
> >
> > Then we can restart vhost-user-blk at any time during VM running.
>
> Sorry is elohimes@gmail.com also an address that belongs to
> Xie Yongji?
>
Yes, that's also my email address.
Thanks,
Yongji
^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [Qemu-devel] [PATCH v6 1/7] vhost-user: Support transferring inflight buffer between qemu and backend
2019-02-18 10:27 ` [Qemu-devel] [PATCH v6 1/7] vhost-user: Support transferring inflight buffer between qemu and backend elohimes
@ 2019-02-21 17:27 ` Michael S. Tsirkin
2019-02-22 2:47 ` Yongji Xie
0 siblings, 1 reply; 18+ messages in thread
From: Michael S. Tsirkin @ 2019-02-21 17:27 UTC (permalink / raw)
To: elohimes
Cc: stefanha, marcandre.lureau, berrange, jasowang, maxime.coquelin,
yury-kotov, wrfsh, qemu-devel, zhangyu31, chaiwen, nixun,
lilin24, Xie Yongji
On Mon, Feb 18, 2019 at 06:27:42PM +0800, elohimes@gmail.com wrote:
> From: Xie Yongji <xieyongji@baidu.com>
>
> This patch introduces two new messages VHOST_USER_GET_INFLIGHT_FD
> and VHOST_USER_SET_INFLIGHT_FD to support transferring a shared
> buffer between qemu and backend.
>
> Firstly, qemu uses VHOST_USER_GET_INFLIGHT_FD to get the
> shared buffer from backend. Then qemu should send it back
> through VHOST_USER_SET_INFLIGHT_FD each time we start vhost-user.
>
> This shared buffer is used to track inflight I/O by backend.
> Qemu should retrieve a new one when vm reset.
>
> Signed-off-by: Xie Yongji <xieyongji@baidu.com>
> Signed-off-by: Chai Wen <chaiwen@baidu.com>
> Signed-off-by: Zhang Yu <zhangyu31@baidu.com>
> ---
> docs/interop/vhost-user.txt | 264 ++++++++++++++++++++++++++++++
> hw/virtio/vhost-user.c | 107 ++++++++++++
> hw/virtio/vhost.c | 96 +++++++++++
> include/hw/virtio/vhost-backend.h | 10 ++
> include/hw/virtio/vhost.h | 18 ++
> 5 files changed, 495 insertions(+)
>
> diff --git a/docs/interop/vhost-user.txt b/docs/interop/vhost-user.txt
> index c2194711d9..61c6d0e415 100644
> --- a/docs/interop/vhost-user.txt
> +++ b/docs/interop/vhost-user.txt
> @@ -142,6 +142,17 @@ Depending on the request type, payload can be:
> Offset: a 64-bit offset of this area from the start of the
> supplied file descriptor
>
> + * Inflight description
> + -----------------------------------------------------
> + | mmap size | mmap offset | num queues | queue size |
> + -----------------------------------------------------
> +
> + mmap size: a 64-bit size of area to track inflight I/O
> + mmap offset: a 64-bit offset of this area from the start
> + of the supplied file descriptor
> + num queues: a 16-bit number of virtqueues
> + queue size: a 16-bit size of virtqueues
> +
> In QEMU the vhost-user message is implemented with the following struct:
>
> typedef struct VhostUserMsg {
> @@ -157,6 +168,7 @@ typedef struct VhostUserMsg {
> struct vhost_iotlb_msg iotlb;
> VhostUserConfig config;
> VhostUserVringArea area;
> + VhostUserInflight inflight;
> };
> } QEMU_PACKED VhostUserMsg;
>
> @@ -175,6 +187,7 @@ the ones that do:
> * VHOST_USER_GET_PROTOCOL_FEATURES
> * VHOST_USER_GET_VRING_BASE
> * VHOST_USER_SET_LOG_BASE (if VHOST_USER_PROTOCOL_F_LOG_SHMFD)
> + * VHOST_USER_GET_INFLIGHT_FD (if VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD)
>
> [ Also see the section on REPLY_ACK protocol extension. ]
>
> @@ -188,6 +201,7 @@ in the ancillary data:
> * VHOST_USER_SET_VRING_CALL
> * VHOST_USER_SET_VRING_ERR
> * VHOST_USER_SET_SLAVE_REQ_FD
> + * VHOST_USER_SET_INFLIGHT_FD (if VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD)
>
> If Master is unable to send the full message or receives a wrong reply it will
> close the connection. An optional reconnection mechanism can be implemented.
> @@ -382,6 +396,235 @@ If VHOST_USER_PROTOCOL_F_SLAVE_SEND_FD protocol feature is negotiated,
> slave can send file descriptors (at most 8 descriptors in each message)
> to master via ancillary data using this fd communication channel.
>
> +Inflight I/O tracking
> +---------------------
> +
> +To support reconnecting after restart or crash, slave may need to resubmit
> +inflight I/Os. If virtqueue is processed in order, we can easily achieve
> +that by getting the inflight descriptors from descriptor table (split virtqueue)
> +or descriptor ring (packed virtqueue). However, it can't work when we process
> +descriptors out-of-order because some entries which store the information of
> +inflight descriptors in available ring (split virtqueue) or descriptor
> +ring (packed virtqueue) might be overrided by new entries. To solve this
> +problem, slave need to allocate an extra buffer to store this information of inflight
> +descriptors and share it with master for persistent. VHOST_USER_GET_INFLIGHT_FD and
> +VHOST_USER_SET_INFLIGHT_FD are used to transfer this buffer between master
> +and slave. And the format of this buffer is described below:
> +
> +-------------------------------------------------------
> +| queue0 region | queue1 region | ... | queueN region |
> +-------------------------------------------------------
> +
> +N is the number of available virtqueues. Slave could get it from num queues
> +field of VhostUserInflight.
> +
> +For split virtqueue, queue region can be implemented as:
> +
> +typedef struct DescStateSplit {
> + /* Indicate whether this descriptor is inflight or not.
> + * Only available for head-descriptor. */
> + uint8_t inflight;
> +
> + /* Padding */
> + uint8_t padding;
> +
> + /* Link to the last processed entry */
> + uint16_t next;
> +} DescStateSplit;
> +
> +typedef struct QueueRegionSplit {
> + /* The feature flags of this region. Now it's initialized to 0. */
> + uint64_t features;
> +
> + /* The version of this region. It's 1 currently.
> + * Zero value indicates an uninitialized buffer */
> + uint16_t version;
> +
> + /* The size of DescStateSplit array. It's equal to the virtqueue
> + * size. Slave could get it from queue size field of VhostUserInflight. */
> + uint16_t desc_num;
> +
> + /* The head of processed DescStateSplit entry list */
> + uint16_t process_head;
> +
> + /* Storing the idx value of used ring */
> + uint16_t used_idx;
> +
> + /* Used to track the state of each descriptor in descriptor table */
> + DescStateSplit desc[0];
> +} QueueRegionSplit;
What is the endian-ness of multibyte fields?
> +
> +To track inflight I/O, the queue region should be processed as follows:
> +
> +When receiving available buffers from the driver:
> +
> + 1. Get the next available head-descriptor index from available ring, i
> +
> + 2. Set desc[i].inflight to 1
> +
> +When supplying used buffers to the driver:
> +
> + 1. Get corresponding used head-descriptor index, i
> +
> + 2. Set desc[i].next to process_head
> +
> + 3. Set process_head to i
> +
> + 4. Steps 1,2,3 may be performed repeatedly if batching is possible
> +
> + 5. Increase the idx value of used ring by the size of the batch
> +
> + 6. Set the inflight field of each DescStateSplit entry in the batch to 0
> +
> + 7. Set used_idx to the idx value of used ring
> +
> +When reconnecting:
> +
> + 1. If the value of used_idx does not match the idx value of used ring,
> +
> + (a) Subtract the value of used_idx from the idx value of used ring to get
> + the number of in-progress DescStateSplit entries
> +
> + (b) Set the inflight field of the in-progress DescStateSplit entries which
> + start from process_head to 0
> +
> + (c) Set used_idx to the idx value of used ring
> +
> + 2. Resubmit each inflight DescStateSplit entry
I re-read a couple of time and I still don't understand what it says.
For simplicity consider split ring. So we want a list of heads that are
outstanding. Fair enough. Now device finishes a head. What now? I needs
to drop head from the list. But list is unidirectional (just next, no
prev). So how can you drop an entry from the middle?
> +For packed virtqueue, queue region can be implemented as:
> +
> +typedef struct DescStatePacked {
> + /* Indicate whether this descriptor is inflight or not.
> + * Only available for head-descriptor. */
> + uint8_t inflight;
> +
> + /* Padding */
> + uint8_t padding;
> +
> + /* Link to the next free entry */
> + uint16_t next;
> +
> + /* Link to the last entry of descriptor list.
> + * Only available for head-descriptor. */
> + uint16_t last;
> +
> + /* The length of descriptor list.
> + * Only available for head-descriptor. */
> + uint16_t num;
> +
> + /* The buffer id */
> + uint16_t id;
> +
> + /* The descriptor flags */
> + uint16_t flags;
> +
> + /* The buffer length */
> + uint32_t len;
> +
> + /* The buffer address */
> + uint64_t addr;
Do we want an extra u64 here to make it a power of two?
> +} DescStatePacked;
> +
> +typedef struct QueueRegionPacked {
> + /* The feature flags of this region. Now it's initialized to 0. */
> + uint64_t features;
> +
> + /* The version of this region. It's 1 currently.
> + * Zero value indicates an uninitialized buffer */
> + uint16_t version;
> +
> + /* The size of DescStatePacked array. It's equal to the virtqueue
> + * size. Slave could get it from queue size field of VhostUserInflight. */
> + uint16_t desc_num;
> +
> + /* The head of free DescStatePacked entry list */
> + uint16_t free_head;
> +
> + /* The old head of free DescStatePacked entry list */
> + uint16_t old_free_head;
> +
> + /* The used index of descriptor ring */
> + uint16_t used_idx;
> +
> + /* The old used index of descriptor ring */
> + uint16_t old_used_idx;
> +
> + /* Device ring wrap counter */
> + uint8_t used_wrap_counter;
> +
> + /* The old device ring wrap counter */
> + uint8_t old_used_wrap_counter;
> +
> + /* Padding */
> + uint8_t padding[7];
> +
> + /* Used to track the state of each descriptor fetched from descriptor ring */
> + DescStatePacked desc[0];
> +} QueueRegionPacked;
> +
> +To track inflight I/O, the queue region should be processed as follows:
> +
> +When receiving available buffers from the driver:
> +
> + 1. Get the next available descriptor entry from descriptor ring, d
> +
> + 2. If d is head descriptor,
> +
> + (a) Set desc[old_free_head].num to 0
> +
> + (b) Set desc[old_free_head].inflight to 1
> +
> + 3. If d is last descriptor, set desc[old_free_head].last to free_head
> +
> + 4. Increase desc[old_free_head].num by 1
> +
> + 5. Set desc[free_head].addr, desc[free_head].len, desc[free_head].flags,
> + desc[free_head].id to d.addr, d.len, d.flags, d.id
> +
> + 6. Set free_head to desc[free_head].next
> +
> + 7. If d is last descriptor, set old_free_head to free_head
> +
> +When supplying used buffers to the driver:
> +
> + 1. Get corresponding used head-descriptor entry from descriptor ring, d
> +
> + 2. Get corresponding DescStatePacked entry, e
> +
> + 3. Set desc[e.last].next to free_head
> +
> + 4. Set free_head to the index of e
> +
> + 5. Steps 1,2,3,4 may be performed repeatedly if batching is possible
> +
> + 6. Increase used_idx by the size of the batch and update used_wrap_counter if needed
> +
> + 7. Update d.flags
> +
> + 8. Set the inflight field of each head DescStatePacked entry in the batch to 0
> +
> + 9. Set old_free_head, old_used_idx, old_used_wrap_counter to free_head, used_idx,
> + used_wrap_counter
> +
> +When reconnecting:
> +
> + 1. If used_idx does not match old_used_idx,
> +
> + (a) Get the next descriptor ring entry through old_used_idx, d
> +
> + (b) Use old_used_wrap_counter to calculate the available flags
> +
> + (c) If d.flags is not equal to the calculated flags value, set old_free_head,
> + old_used_idx, old_used_wrap_counter to free_head, used_idx, used_wrap_counter
> +
> + 2. Set free_head, used_idx, used_wrap_counter to old_free_head, old_used_idx,
> + old_used_wrap_counter
> +
> + 3. Set the inflight field of each free DescStatePacked entry to 0
> +
> + 4. Resubmit each inflight DescStatePacked entry
> +
> Protocol features
> -----------------
>
> @@ -397,6 +640,7 @@ Protocol features
> #define VHOST_USER_PROTOCOL_F_CONFIG 9
> #define VHOST_USER_PROTOCOL_F_SLAVE_SEND_FD 10
> #define VHOST_USER_PROTOCOL_F_HOST_NOTIFIER 11
> +#define VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD 12
>
> Master message types
> --------------------
> @@ -761,6 +1005,26 @@ Master message types
> was previously sent.
> The value returned is an error indication; 0 is success.
>
> + * VHOST_USER_GET_INFLIGHT_FD
> + Id: 31
> + Equivalent ioctl: N/A
> + Master payload: inflight description
> +
> + When VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD protocol feature has been
> + successfully negotiated, this message is submitted by master to get
> + a shared buffer from slave. The shared buffer will be used to track
> + inflight I/O by slave. QEMU should retrieve a new one when vm reset.
> +
> + * VHOST_USER_SET_INFLIGHT_FD
> + Id: 32
> + Equivalent ioctl: N/A
> + Master payload: inflight description
> +
> + When VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD protocol feature has been
> + successfully negotiated, this message is submitted by master to send
> + the shared inflight buffer back to slave so that slave could get
> + inflight I/O after a crash or restart.
> +
> Slave message types
> -------------------
>
> diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
> index 564a31d12c..21a81998ba 100644
> --- a/hw/virtio/vhost-user.c
> +++ b/hw/virtio/vhost-user.c
> @@ -52,6 +52,7 @@ enum VhostUserProtocolFeature {
> VHOST_USER_PROTOCOL_F_CONFIG = 9,
> VHOST_USER_PROTOCOL_F_SLAVE_SEND_FD = 10,
> VHOST_USER_PROTOCOL_F_HOST_NOTIFIER = 11,
> + VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD = 12,
> VHOST_USER_PROTOCOL_F_MAX
> };
>
> @@ -89,6 +90,8 @@ typedef enum VhostUserRequest {
> VHOST_USER_POSTCOPY_ADVISE = 28,
> VHOST_USER_POSTCOPY_LISTEN = 29,
> VHOST_USER_POSTCOPY_END = 30,
> + VHOST_USER_GET_INFLIGHT_FD = 31,
> + VHOST_USER_SET_INFLIGHT_FD = 32,
> VHOST_USER_MAX
> } VhostUserRequest;
>
> @@ -147,6 +150,13 @@ typedef struct VhostUserVringArea {
> uint64_t offset;
> } VhostUserVringArea;
>
> +typedef struct VhostUserInflight {
> + uint64_t mmap_size;
> + uint64_t mmap_offset;
> + uint16_t num_queues;
> + uint16_t queue_size;
> +} VhostUserInflight;
> +
> typedef struct {
> VhostUserRequest request;
>
> @@ -169,6 +179,7 @@ typedef union {
> VhostUserConfig config;
> VhostUserCryptoSession session;
> VhostUserVringArea area;
> + VhostUserInflight inflight;
> } VhostUserPayload;
>
> typedef struct VhostUserMsg {
> @@ -1739,6 +1750,100 @@ static bool vhost_user_mem_section_filter(struct vhost_dev *dev,
> return result;
> }
>
> +static int vhost_user_get_inflight_fd(struct vhost_dev *dev,
> + uint16_t queue_size,
> + struct vhost_inflight *inflight)
> +{
> + void *addr;
> + int fd;
> + struct vhost_user *u = dev->opaque;
> + CharBackend *chr = u->user->chr;
> + VhostUserMsg msg = {
> + .hdr.request = VHOST_USER_GET_INFLIGHT_FD,
> + .hdr.flags = VHOST_USER_VERSION,
> + .payload.inflight.num_queues = dev->nvqs,
> + .payload.inflight.queue_size = queue_size,
> + .hdr.size = sizeof(msg.payload.inflight),
> + };
> +
> + if (!virtio_has_feature(dev->protocol_features,
> + VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD)) {
> + return 0;
> + }
> +
> + if (vhost_user_write(dev, &msg, NULL, 0) < 0) {
> + return -1;
> + }
> +
> + if (vhost_user_read(dev, &msg) < 0) {
> + return -1;
> + }
> +
> + if (msg.hdr.request != VHOST_USER_GET_INFLIGHT_FD) {
> + error_report("Received unexpected msg type. "
> + "Expected %d received %d",
> + VHOST_USER_GET_INFLIGHT_FD, msg.hdr.request);
> + return -1;
> + }
> +
> + if (msg.hdr.size != sizeof(msg.payload.inflight)) {
> + error_report("Received bad msg size.");
> + return -1;
> + }
> +
> + if (!msg.payload.inflight.mmap_size) {
> + return 0;
> + }
> +
> + fd = qemu_chr_fe_get_msgfd(chr);
> + if (fd < 0) {
> + error_report("Failed to get mem fd");
> + return -1;
> + }
> +
> + addr = mmap(0, msg.payload.inflight.mmap_size, PROT_READ | PROT_WRITE,
> + MAP_SHARED, fd, msg.payload.inflight.mmap_offset);
> +
> + if (addr == MAP_FAILED) {
> + error_report("Failed to mmap mem fd");
> + close(fd);
> + return -1;
> + }
> +
> + inflight->addr = addr;
> + inflight->fd = fd;
> + inflight->size = msg.payload.inflight.mmap_size;
> + inflight->offset = msg.payload.inflight.mmap_offset;
> + inflight->queue_size = queue_size;
> +
> + return 0;
> +}
> +
> +static int vhost_user_set_inflight_fd(struct vhost_dev *dev,
> + struct vhost_inflight *inflight)
> +{
> + VhostUserMsg msg = {
> + .hdr.request = VHOST_USER_SET_INFLIGHT_FD,
> + .hdr.flags = VHOST_USER_VERSION,
> + .payload.inflight.mmap_size = inflight->size,
> + .payload.inflight.mmap_offset = inflight->offset,
> + .payload.inflight.num_queues = dev->nvqs,
> + .payload.inflight.queue_size = inflight->queue_size,
> + .hdr.size = sizeof(msg.payload.inflight),
> + };
> +
> + if (!virtio_has_feature(dev->protocol_features,
> + VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD)) {
> + return 0;
> + }
> +
> + if (vhost_user_write(dev, &msg, &inflight->fd, 1) < 0) {
> + return -1;
> + }
> +
> + return 0;
> +}
> +
> VhostUserState *vhost_user_init(void)
> {
> VhostUserState *user = g_new0(struct VhostUserState, 1);
> @@ -1790,4 +1895,6 @@ const VhostOps user_ops = {
> .vhost_crypto_create_session = vhost_user_crypto_create_session,
> .vhost_crypto_close_session = vhost_user_crypto_close_session,
> .vhost_backend_mem_section_filter = vhost_user_mem_section_filter,
> + .vhost_get_inflight_fd = vhost_user_get_inflight_fd,
> + .vhost_set_inflight_fd = vhost_user_set_inflight_fd,
> };
> diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
> index 569c4053ea..8db1a855eb 100644
> --- a/hw/virtio/vhost.c
> +++ b/hw/virtio/vhost.c
> @@ -1481,6 +1481,102 @@ void vhost_dev_set_config_notifier(struct vhost_dev *hdev,
> hdev->config_ops = ops;
> }
>
> +void vhost_dev_free_inflight(struct vhost_inflight *inflight)
> +{
> + if (inflight->addr) {
> + qemu_memfd_free(inflight->addr, inflight->size, inflight->fd);
> + inflight->addr = NULL;
> + inflight->fd = -1;
> + }
> +}
> +
> +static int vhost_dev_resize_inflight(struct vhost_inflight *inflight,
> + uint64_t new_size)
> +{
> + Error *err = NULL;
> + int fd = -1;
> + void *addr = qemu_memfd_alloc("vhost-inflight", new_size,
> + F_SEAL_GROW | F_SEAL_SHRINK | F_SEAL_SEAL,
> + &fd, &err);
> +
> + if (err) {
> + error_report_err(err);
> + return -1;
> + }
> +
> + vhost_dev_free_inflight(inflight);
> + inflight->offset = 0;
> + inflight->addr = addr;
> + inflight->fd = fd;
> + inflight->size = new_size;
> +
> + return 0;
> +}
> +
> +void vhost_dev_save_inflight(struct vhost_inflight *inflight, QEMUFile *f)
> +{
> + if (inflight->addr) {
> + qemu_put_be64(f, inflight->size);
> + qemu_put_be16(f, inflight->queue_size);
> + qemu_put_buffer(f, inflight->addr, inflight->size);
> + } else {
> + qemu_put_be64(f, 0);
> + }
> +}
> +
> +int vhost_dev_load_inflight(struct vhost_inflight *inflight, QEMUFile *f)
> +{
> + uint64_t size;
> +
> + size = qemu_get_be64(f);
> + if (!size) {
> + return 0;
> + }
> +
> + if (inflight->size != size) {
> + if (vhost_dev_resize_inflight(inflight, size)) {
> + return -1;
> + }
> + }
> + inflight->queue_size = qemu_get_be16(f);
> +
> + qemu_get_buffer(f, inflight->addr, size);
> +
> + return 0;
> +}
> +
> +int vhost_dev_set_inflight(struct vhost_dev *dev,
> + struct vhost_inflight *inflight)
> +{
> + int r;
> +
> + if (dev->vhost_ops->vhost_set_inflight_fd && inflight->addr) {
> + r = dev->vhost_ops->vhost_set_inflight_fd(dev, inflight);
> + if (r) {
> + VHOST_OPS_DEBUG("vhost_set_inflight_fd failed");
> + return -errno;
> + }
> + }
> +
> + return 0;
> +}
> +
> +int vhost_dev_get_inflight(struct vhost_dev *dev, uint16_t queue_size,
> + struct vhost_inflight *inflight)
> +{
> + int r;
> +
> + if (dev->vhost_ops->vhost_get_inflight_fd) {
> + r = dev->vhost_ops->vhost_get_inflight_fd(dev, queue_size, inflight);
> + if (r) {
> + VHOST_OPS_DEBUG("vhost_get_inflight_fd failed");
> + return -errno;
> + }
> + }
> +
> + return 0;
> +}
> +
> /* Host notifiers must be enabled at this point. */
> int vhost_dev_start(struct vhost_dev *hdev, VirtIODevice *vdev)
> {
> diff --git a/include/hw/virtio/vhost-backend.h b/include/hw/virtio/vhost-backend.h
> index 81283ec50f..d6632a18e6 100644
> --- a/include/hw/virtio/vhost-backend.h
> +++ b/include/hw/virtio/vhost-backend.h
> @@ -25,6 +25,7 @@ typedef enum VhostSetConfigType {
> VHOST_SET_CONFIG_TYPE_MIGRATION = 1,
> } VhostSetConfigType;
>
> +struct vhost_inflight;
> struct vhost_dev;
> struct vhost_log;
> struct vhost_memory;
> @@ -104,6 +105,13 @@ typedef int (*vhost_crypto_close_session_op)(struct vhost_dev *dev,
> typedef bool (*vhost_backend_mem_section_filter_op)(struct vhost_dev *dev,
> MemoryRegionSection *section);
>
> +typedef int (*vhost_get_inflight_fd_op)(struct vhost_dev *dev,
> + uint16_t queue_size,
> + struct vhost_inflight *inflight);
> +
> +typedef int (*vhost_set_inflight_fd_op)(struct vhost_dev *dev,
> + struct vhost_inflight *inflight);
> +
> typedef struct VhostOps {
> VhostBackendType backend_type;
> vhost_backend_init vhost_backend_init;
> @@ -142,6 +150,8 @@ typedef struct VhostOps {
> vhost_crypto_create_session_op vhost_crypto_create_session;
> vhost_crypto_close_session_op vhost_crypto_close_session;
> vhost_backend_mem_section_filter_op vhost_backend_mem_section_filter;
> + vhost_get_inflight_fd_op vhost_get_inflight_fd;
> + vhost_set_inflight_fd_op vhost_set_inflight_fd;
> } VhostOps;
>
> extern const VhostOps user_ops;
> diff --git a/include/hw/virtio/vhost.h b/include/hw/virtio/vhost.h
> index a7f449fa87..619498c8f4 100644
> --- a/include/hw/virtio/vhost.h
> +++ b/include/hw/virtio/vhost.h
> @@ -7,6 +7,15 @@
> #include "exec/memory.h"
>
> /* Generic structures common for any vhost based device. */
> +
> +struct vhost_inflight {
> + int fd;
> + void *addr;
> + uint64_t size;
> + uint64_t offset;
> + uint16_t queue_size;
> +};
> +
> struct vhost_virtqueue {
> int kick;
> int call;
> @@ -120,4 +129,13 @@ int vhost_dev_set_config(struct vhost_dev *dev, const uint8_t *data,
> */
> void vhost_dev_set_config_notifier(struct vhost_dev *dev,
> const VhostDevConfigOps *ops);
> +
> +void vhost_dev_reset_inflight(struct vhost_inflight *inflight);
> +void vhost_dev_free_inflight(struct vhost_inflight *inflight);
> +void vhost_dev_save_inflight(struct vhost_inflight *inflight, QEMUFile *f);
> +int vhost_dev_load_inflight(struct vhost_inflight *inflight, QEMUFile *f);
> +int vhost_dev_set_inflight(struct vhost_dev *dev,
> + struct vhost_inflight *inflight);
> +int vhost_dev_get_inflight(struct vhost_dev *dev, uint16_t queue_size,
> + struct vhost_inflight *inflight);
> #endif
> --
> 2.17.1
^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [Qemu-devel] [PATCH v6 1/7] vhost-user: Support transferring inflight buffer between qemu and backend
2019-02-21 17:27 ` Michael S. Tsirkin
@ 2019-02-22 2:47 ` Yongji Xie
2019-02-22 6:21 ` Michael S. Tsirkin
0 siblings, 1 reply; 18+ messages in thread
From: Yongji Xie @ 2019-02-22 2:47 UTC (permalink / raw)
To: Michael S. Tsirkin
Cc: Stefan Hajnoczi, Marc-André Lureau, Daniel P. Berrangé,
Jason Wang, Coquelin, Maxime, Yury Kotov,
Евгений
Яковлев,
qemu-devel, zhangyu31, chaiwen, nixun, lilin24, Xie Yongji
On Fri, 22 Feb 2019 at 01:27, Michael S. Tsirkin <mst@redhat.com> wrote:
>
> On Mon, Feb 18, 2019 at 06:27:42PM +0800, elohimes@gmail.com wrote:
> > From: Xie Yongji <xieyongji@baidu.com>
> >
> > This patch introduces two new messages VHOST_USER_GET_INFLIGHT_FD
> > and VHOST_USER_SET_INFLIGHT_FD to support transferring a shared
> > buffer between qemu and backend.
> >
> > Firstly, qemu uses VHOST_USER_GET_INFLIGHT_FD to get the
> > shared buffer from backend. Then qemu should send it back
> > through VHOST_USER_SET_INFLIGHT_FD each time we start vhost-user.
> >
> > This shared buffer is used to track inflight I/O by backend.
> > Qemu should retrieve a new one when vm reset.
> >
> > Signed-off-by: Xie Yongji <xieyongji@baidu.com>
> > Signed-off-by: Chai Wen <chaiwen@baidu.com>
> > Signed-off-by: Zhang Yu <zhangyu31@baidu.com>
> > ---
> > docs/interop/vhost-user.txt | 264 ++++++++++++++++++++++++++++++
> > hw/virtio/vhost-user.c | 107 ++++++++++++
> > hw/virtio/vhost.c | 96 +++++++++++
> > include/hw/virtio/vhost-backend.h | 10 ++
> > include/hw/virtio/vhost.h | 18 ++
> > 5 files changed, 495 insertions(+)
> >
> > diff --git a/docs/interop/vhost-user.txt b/docs/interop/vhost-user.txt
> > index c2194711d9..61c6d0e415 100644
> > --- a/docs/interop/vhost-user.txt
> > +++ b/docs/interop/vhost-user.txt
> > @@ -142,6 +142,17 @@ Depending on the request type, payload can be:
> > Offset: a 64-bit offset of this area from the start of the
> > supplied file descriptor
> >
> > + * Inflight description
> > + -----------------------------------------------------
> > + | mmap size | mmap offset | num queues | queue size |
> > + -----------------------------------------------------
> > +
> > + mmap size: a 64-bit size of area to track inflight I/O
> > + mmap offset: a 64-bit offset of this area from the start
> > + of the supplied file descriptor
> > + num queues: a 16-bit number of virtqueues
> > + queue size: a 16-bit size of virtqueues
> > +
> > In QEMU the vhost-user message is implemented with the following struct:
> >
> > typedef struct VhostUserMsg {
> > @@ -157,6 +168,7 @@ typedef struct VhostUserMsg {
> > struct vhost_iotlb_msg iotlb;
> > VhostUserConfig config;
> > VhostUserVringArea area;
> > + VhostUserInflight inflight;
> > };
> > } QEMU_PACKED VhostUserMsg;
> >
> > @@ -175,6 +187,7 @@ the ones that do:
> > * VHOST_USER_GET_PROTOCOL_FEATURES
> > * VHOST_USER_GET_VRING_BASE
> > * VHOST_USER_SET_LOG_BASE (if VHOST_USER_PROTOCOL_F_LOG_SHMFD)
> > + * VHOST_USER_GET_INFLIGHT_FD (if VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD)
> >
> > [ Also see the section on REPLY_ACK protocol extension. ]
> >
> > @@ -188,6 +201,7 @@ in the ancillary data:
> > * VHOST_USER_SET_VRING_CALL
> > * VHOST_USER_SET_VRING_ERR
> > * VHOST_USER_SET_SLAVE_REQ_FD
> > + * VHOST_USER_SET_INFLIGHT_FD (if VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD)
> >
> > If Master is unable to send the full message or receives a wrong reply it will
> > close the connection. An optional reconnection mechanism can be implemented.
> > @@ -382,6 +396,235 @@ If VHOST_USER_PROTOCOL_F_SLAVE_SEND_FD protocol feature is negotiated,
> > slave can send file descriptors (at most 8 descriptors in each message)
> > to master via ancillary data using this fd communication channel.
> >
> > +Inflight I/O tracking
> > +---------------------
> > +
> > +To support reconnecting after restart or crash, slave may need to resubmit
> > +inflight I/Os. If virtqueue is processed in order, we can easily achieve
> > +that by getting the inflight descriptors from descriptor table (split virtqueue)
> > +or descriptor ring (packed virtqueue). However, it can't work when we process
> > +descriptors out-of-order because some entries which store the information of
> > +inflight descriptors in available ring (split virtqueue) or descriptor
> > +ring (packed virtqueue) might be overrided by new entries. To solve this
> > +problem, slave need to allocate an extra buffer to store this information of inflight
> > +descriptors and share it with master for persistent. VHOST_USER_GET_INFLIGHT_FD and
> > +VHOST_USER_SET_INFLIGHT_FD are used to transfer this buffer between master
> > +and slave. And the format of this buffer is described below:
> > +
> > +-------------------------------------------------------
> > +| queue0 region | queue1 region | ... | queueN region |
> > +-------------------------------------------------------
> > +
> > +N is the number of available virtqueues. Slave could get it from num queues
> > +field of VhostUserInflight.
> > +
> > +For split virtqueue, queue region can be implemented as:
> > +
> > +typedef struct DescStateSplit {
> > + /* Indicate whether this descriptor is inflight or not.
> > + * Only available for head-descriptor. */
> > + uint8_t inflight;
> > +
> > + /* Padding */
> > + uint8_t padding;
> > +
> > + /* Link to the last processed entry */
> > + uint16_t next;
> > +} DescStateSplit;
> > +
> > +typedef struct QueueRegionSplit {
> > + /* The feature flags of this region. Now it's initialized to 0. */
> > + uint64_t features;
> > +
> > + /* The version of this region. It's 1 currently.
> > + * Zero value indicates an uninitialized buffer */
> > + uint16_t version;
> > +
> > + /* The size of DescStateSplit array. It's equal to the virtqueue
> > + * size. Slave could get it from queue size field of VhostUserInflight. */
> > + uint16_t desc_num;
> > +
> > + /* The head of processed DescStateSplit entry list */
> > + uint16_t process_head;
> > +
> > + /* Storing the idx value of used ring */
> > + uint16_t used_idx;
> > +
> > + /* Used to track the state of each descriptor in descriptor table */
> > + DescStateSplit desc[0];
> > +} QueueRegionSplit;
>
>
> What is the endian-ness of multibyte fields?
>
Native endian is OK here. Right?
>
> > +
> > +To track inflight I/O, the queue region should be processed as follows:
> > +
> > +When receiving available buffers from the driver:
> > +
> > + 1. Get the next available head-descriptor index from available ring, i
> > +
> > + 2. Set desc[i].inflight to 1
> > +
> > +When supplying used buffers to the driver:
> > +
> > + 1. Get corresponding used head-descriptor index, i
> > +
> > + 2. Set desc[i].next to process_head
> > +
> > + 3. Set process_head to i
> > +
> > + 4. Steps 1,2,3 may be performed repeatedly if batching is possible
> > +
> > + 5. Increase the idx value of used ring by the size of the batch
> > +
> > + 6. Set the inflight field of each DescStateSplit entry in the batch to 0
> > +
> > + 7. Set used_idx to the idx value of used ring
> > +
> > +When reconnecting:
> > +
> > + 1. If the value of used_idx does not match the idx value of used ring,
> > +
> > + (a) Subtract the value of used_idx from the idx value of used ring to get
> > + the number of in-progress DescStateSplit entries
> > +
> > + (b) Set the inflight field of the in-progress DescStateSplit entries which
> > + start from process_head to 0
> > +
> > + (c) Set used_idx to the idx value of used ring
> > +
> > + 2. Resubmit each inflight DescStateSplit entry
>
> I re-read a couple of time and I still don't understand what it says.
>
> For simplicity consider split ring. So we want a list of heads that are
> outstanding. Fair enough. Now device finishes a head. What now? I needs
> to drop head from the list. But list is unidirectional (just next, no
> prev). So how can you drop an entry from the middle?
>
The process_head is only used when slave crash between increasing the
idx value of used ring and updating used_idx. We use it to find the
in-progress DescStateSplit entries before the crash and complete them
when reconnecting. Make sure guest and slave have the same view for
inflight I/Os.
In other case, the inflight field is enough to track inflight I/O.
When reconnecting, we go through all DescStateSplit entries and
re-submit the entry whose inflight field is equal to 1.
> > +For packed virtqueue, queue region can be implemented as:
> > +
> > +typedef struct DescStatePacked {
> > + /* Indicate whether this descriptor is inflight or not.
> > + * Only available for head-descriptor. */
> > + uint8_t inflight;
> > +
> > + /* Padding */
> > + uint8_t padding;
> > +
> > + /* Link to the next free entry */
> > + uint16_t next;
> > +
> > + /* Link to the last entry of descriptor list.
> > + * Only available for head-descriptor. */
> > + uint16_t last;
> > +
> > + /* The length of descriptor list.
> > + * Only available for head-descriptor. */
> > + uint16_t num;
> > +
> > + /* The buffer id */
> > + uint16_t id;
> > +
> > + /* The descriptor flags */
> > + uint16_t flags;
> > +
> > + /* The buffer length */
> > + uint32_t len;
> > +
> > + /* The buffer address */
> > + uint64_t addr;
>
> Do we want an extra u64 here to make it a power of two?
>
Looks good to me.
Thanks,
Yongji
^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [Qemu-devel] [PATCH v6 1/7] vhost-user: Support transferring inflight buffer between qemu and backend
2019-02-22 2:47 ` Yongji Xie
@ 2019-02-22 6:21 ` Michael S. Tsirkin
2019-02-22 7:05 ` Yongji Xie
0 siblings, 1 reply; 18+ messages in thread
From: Michael S. Tsirkin @ 2019-02-22 6:21 UTC (permalink / raw)
To: Yongji Xie
Cc: Stefan Hajnoczi, Marc-André Lureau, Daniel P. Berrangé,
Jason Wang, Coquelin, Maxime, Yury Kotov,
Евгений
Яковлев,
qemu-devel, zhangyu31, chaiwen, nixun, lilin24, Xie Yongji
On Fri, Feb 22, 2019 at 10:47:03AM +0800, Yongji Xie wrote:
> > > +
> > > +To track inflight I/O, the queue region should be processed as follows:
> > > +
> > > +When receiving available buffers from the driver:
> > > +
> > > + 1. Get the next available head-descriptor index from available ring, i
> > > +
> > > + 2. Set desc[i].inflight to 1
> > > +
> > > +When supplying used buffers to the driver:
> > > +
> > > + 1. Get corresponding used head-descriptor index, i
> > > +
> > > + 2. Set desc[i].next to process_head
> > > +
> > > + 3. Set process_head to i
> > > +
> > > + 4. Steps 1,2,3 may be performed repeatedly if batching is possible
> > > +
> > > + 5. Increase the idx value of used ring by the size of the batch
> > > +
> > > + 6. Set the inflight field of each DescStateSplit entry in the batch to 0
> > > +
> > > + 7. Set used_idx to the idx value of used ring
> > > +
> > > +When reconnecting:
> > > +
> > > + 1. If the value of used_idx does not match the idx value of used ring,
> > > +
> > > + (a) Subtract the value of used_idx from the idx value of used ring to get
> > > + the number of in-progress DescStateSplit entries
> > > +
> > > + (b) Set the inflight field of the in-progress DescStateSplit entries which
> > > + start from process_head to 0
> > > +
> > > + (c) Set used_idx to the idx value of used ring
> > > +
> > > + 2. Resubmit each inflight DescStateSplit entry
> >
> > I re-read a couple of time and I still don't understand what it says.
> >
> > For simplicity consider split ring. So we want a list of heads that are
> > outstanding. Fair enough. Now device finishes a head. What now? I needs
> > to drop head from the list. But list is unidirectional (just next, no
> > prev). So how can you drop an entry from the middle?
> >
>
> The process_head is only used when slave crash between increasing the
> idx value of used ring and updating used_idx. We use it to find the
> in-progress DescStateSplit entries before the crash and complete them
> when reconnecting. Make sure guest and slave have the same view for
> inflight I/Os.
>
But I don't understand how does the described process help do it?
> In other case, the inflight field is enough to track inflight I/O.
> When reconnecting, we go through all DescStateSplit entries and
> re-submit the entry whose inflight field is equal to 1.
What I don't understand is how do we know the order
in which they have to be resubmitted. Reordering
operations would be a big problem, won't it?
Let's say I fetch descriptors A, B, C and start
processing. how does memory look?
Now I finished B and marked it used. How does
memory look?
I also wonder how do you address a crash between
marking descriptor used and clearing inflight.
Will you redo the descriptor? Is it always safe?
What if it's a write?
^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [Qemu-devel] [PATCH v6 1/7] vhost-user: Support transferring inflight buffer between qemu and backend
2019-02-22 6:21 ` Michael S. Tsirkin
@ 2019-02-22 7:05 ` Yongji Xie
2019-02-22 14:54 ` Michael S. Tsirkin
0 siblings, 1 reply; 18+ messages in thread
From: Yongji Xie @ 2019-02-22 7:05 UTC (permalink / raw)
To: Michael S. Tsirkin
Cc: Stefan Hajnoczi, Marc-André Lureau, Daniel P. Berrangé,
Jason Wang, Coquelin, Maxime, Yury Kotov,
Евгений
Яковлев,
qemu-devel, zhangyu31, chaiwen, nixun, lilin24, Xie Yongji
On Fri, 22 Feb 2019 at 14:21, Michael S. Tsirkin <mst@redhat.com> wrote:
>
> On Fri, Feb 22, 2019 at 10:47:03AM +0800, Yongji Xie wrote:
> > > > +
> > > > +To track inflight I/O, the queue region should be processed as follows:
> > > > +
> > > > +When receiving available buffers from the driver:
> > > > +
> > > > + 1. Get the next available head-descriptor index from available ring, i
> > > > +
> > > > + 2. Set desc[i].inflight to 1
> > > > +
> > > > +When supplying used buffers to the driver:
> > > > +
> > > > + 1. Get corresponding used head-descriptor index, i
> > > > +
> > > > + 2. Set desc[i].next to process_head
> > > > +
> > > > + 3. Set process_head to i
> > > > +
> > > > + 4. Steps 1,2,3 may be performed repeatedly if batching is possible
> > > > +
> > > > + 5. Increase the idx value of used ring by the size of the batch
> > > > +
> > > > + 6. Set the inflight field of each DescStateSplit entry in the batch to 0
> > > > +
> > > > + 7. Set used_idx to the idx value of used ring
> > > > +
> > > > +When reconnecting:
> > > > +
> > > > + 1. If the value of used_idx does not match the idx value of used ring,
> > > > +
> > > > + (a) Subtract the value of used_idx from the idx value of used ring to get
> > > > + the number of in-progress DescStateSplit entries
> > > > +
> > > > + (b) Set the inflight field of the in-progress DescStateSplit entries which
> > > > + start from process_head to 0
> > > > +
> > > > + (c) Set used_idx to the idx value of used ring
> > > > +
> > > > + 2. Resubmit each inflight DescStateSplit entry
> > >
> > > I re-read a couple of time and I still don't understand what it says.
> > >
> > > For simplicity consider split ring. So we want a list of heads that are
> > > outstanding. Fair enough. Now device finishes a head. What now? I needs
> > > to drop head from the list. But list is unidirectional (just next, no
> > > prev). So how can you drop an entry from the middle?
> > >
> >
> > The process_head is only used when slave crash between increasing the
> > idx value of used ring and updating used_idx. We use it to find the
> > in-progress DescStateSplit entries before the crash and complete them
> > when reconnecting. Make sure guest and slave have the same view for
> > inflight I/Os.
> >
>
> But I don't understand how does the described process help do it?
>
For example, we need to submit descriptors A, B, C to driver in a batch.
Firstly, we will link those descriptors like:
process_head->A->B->C (A)
Then, we need to update idx value of used vring to mark those
descriptors as used:
_vring.used->idx += 3 (B)
At last, clear the inflight field of those descriptors and update
used_idx field:
A.inflight = 0; B.inflight = 0; C.inflight = 0; (C)
used_idx = _vring.used->idx; (D)
After (B), guest can consume the descriptors A,B,C. So we must make
sure the inflight field of A,B,C is cleared when reconnecting to avoid
re-submitting used descriptor. If slave crash during (C), the inflight
field of A,B,C may be incorrect. To detect that case, we can see
whether used_idx matches _vring.used->idx. And through process_head,
we can get the in-progress descriptors A,B,C and clear their inflight
field again when reconnecting.
>
> > In other case, the inflight field is enough to track inflight I/O.
> > When reconnecting, we go through all DescStateSplit entries and
> > re-submit the entry whose inflight field is equal to 1.
>
> What I don't understand is how do we know the order
> in which they have to be resubmitted. Reordering
> operations would be a big problem, won't it?
>
In previous patch, I record avail_idx for each DescStateSplit entry to
preserve the order. Is it useful to fix this?
>
> Let's say I fetch descriptors A, B, C and start
> processing. how does memory look?
A.inflight = 1, C.inflight = 1, B.inflight = 1
> Now I finished B and marked it used. How does
> memory look?
>
A.inflight = 1, C.inflight = 1, B.inflight = 0, process_head = B
> I also wonder how do you address a crash between
> marking descriptor used and clearing inflight.
> Will you redo the descriptor? Is it always safe?
> What if it's a write?
>
It's safe. We can get the in-progess descriptors through process_head
and clear their inflight field when reconnecting.
Thanks,
Yongji
^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [Qemu-devel] [PATCH v6 1/7] vhost-user: Support transferring inflight buffer between qemu and backend
2019-02-22 7:05 ` Yongji Xie
@ 2019-02-22 14:54 ` Michael S. Tsirkin
2019-02-23 13:10 ` Yongji Xie
0 siblings, 1 reply; 18+ messages in thread
From: Michael S. Tsirkin @ 2019-02-22 14:54 UTC (permalink / raw)
To: Yongji Xie
Cc: Stefan Hajnoczi, Marc-André Lureau, Daniel P. Berrangé,
Jason Wang, Coquelin, Maxime, Yury Kotov,
Евгений
Яковлев,
qemu-devel, zhangyu31, chaiwen, nixun, lilin24, Xie Yongji
On Fri, Feb 22, 2019 at 03:05:23PM +0800, Yongji Xie wrote:
> On Fri, 22 Feb 2019 at 14:21, Michael S. Tsirkin <mst@redhat.com> wrote:
> >
> > On Fri, Feb 22, 2019 at 10:47:03AM +0800, Yongji Xie wrote:
> > > > > +
> > > > > +To track inflight I/O, the queue region should be processed as follows:
> > > > > +
> > > > > +When receiving available buffers from the driver:
> > > > > +
> > > > > + 1. Get the next available head-descriptor index from available ring, i
> > > > > +
> > > > > + 2. Set desc[i].inflight to 1
> > > > > +
> > > > > +When supplying used buffers to the driver:
> > > > > +
> > > > > + 1. Get corresponding used head-descriptor index, i
> > > > > +
> > > > > + 2. Set desc[i].next to process_head
> > > > > +
> > > > > + 3. Set process_head to i
> > > > > +
> > > > > + 4. Steps 1,2,3 may be performed repeatedly if batching is possible
> > > > > +
> > > > > + 5. Increase the idx value of used ring by the size of the batch
> > > > > +
> > > > > + 6. Set the inflight field of each DescStateSplit entry in the batch to 0
> > > > > +
> > > > > + 7. Set used_idx to the idx value of used ring
> > > > > +
> > > > > +When reconnecting:
> > > > > +
> > > > > + 1. If the value of used_idx does not match the idx value of used ring,
> > > > > +
> > > > > + (a) Subtract the value of used_idx from the idx value of used ring to get
> > > > > + the number of in-progress DescStateSplit entries
> > > > > +
> > > > > + (b) Set the inflight field of the in-progress DescStateSplit entries which
> > > > > + start from process_head to 0
> > > > > +
> > > > > + (c) Set used_idx to the idx value of used ring
> > > > > +
> > > > > + 2. Resubmit each inflight DescStateSplit entry
> > > >
> > > > I re-read a couple of time and I still don't understand what it says.
> > > >
> > > > For simplicity consider split ring. So we want a list of heads that are
> > > > outstanding. Fair enough. Now device finishes a head. What now? I needs
> > > > to drop head from the list. But list is unidirectional (just next, no
> > > > prev). So how can you drop an entry from the middle?
> > > >
> > >
> > > The process_head is only used when slave crash between increasing the
> > > idx value of used ring and updating used_idx. We use it to find the
> > > in-progress DescStateSplit entries before the crash and complete them
> > > when reconnecting. Make sure guest and slave have the same view for
> > > inflight I/Os.
> > >
> >
> > But I don't understand how does the described process help do it?
> >
>
> For example, we need to submit descriptors A, B, C to driver in a batch.
>
> Firstly, we will link those descriptors like:
>
> process_head->A->B->C (A)
>
> Then, we need to update idx value of used vring to mark those
> descriptors as used:
>
> _vring.used->idx += 3 (B)
>
> At last, clear the inflight field of those descriptors and update
> used_idx field:
>
> A.inflight = 0; B.inflight = 0; C.inflight = 0; (C)
>
> used_idx = _vring.used->idx; (D)
>
> After (B), guest can consume the descriptors A,B,C. So we must make
> sure the inflight field of A,B,C is cleared when reconnecting to avoid
> re-submitting used descriptor. If slave crash during (C), the inflight
> field of A,B,C may be incorrect. To detect that case, we can see
> whether used_idx matches _vring.used->idx. And through process_head,
> we can get the in-progress descriptors A,B,C and clear their inflight
> field again when reconnecting.
>
> >
> > > In other case, the inflight field is enough to track inflight I/O.
> > > When reconnecting, we go through all DescStateSplit entries and
> > > re-submit the entry whose inflight field is equal to 1.
> >
> > What I don't understand is how do we know the order
> > in which they have to be resubmitted. Reordering
> > operations would be a big problem, won't it?
> >
>
> In previous patch, I record avail_idx for each DescStateSplit entry to
> preserve the order. Is it useful to fix this?
>
> >
> > Let's say I fetch descriptors A, B, C and start
> > processing. how does memory look?
>
> A.inflight = 1, C.inflight = 1, B.inflight = 1
>
> > Now I finished B and marked it used. How does
> > memory look?
> >
>
> A.inflight = 1, C.inflight = 1, B.inflight = 0, process_head = B
OK. And we have
process_head->B->process_head
?
Now if there is a reconnect, I want to submit A and then C,
correct? How do I know that from this picture? How do I
know to start with A? It's not on the list anymore...
> > I also wonder how do you address a crash between
> > marking descriptor used and clearing inflight.
> > Will you redo the descriptor? Is it always safe?
> > What if it's a write?
> >
>
> It's safe. We can get the in-progess descriptors through process_head
> and clear their inflight field when reconnecting.
>
> Thanks,
> Yongji
^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [Qemu-devel] [PATCH v6 1/7] vhost-user: Support transferring inflight buffer between qemu and backend
2019-02-22 14:54 ` Michael S. Tsirkin
@ 2019-02-23 13:10 ` Yongji Xie
2019-02-24 0:14 ` Michael S. Tsirkin
0 siblings, 1 reply; 18+ messages in thread
From: Yongji Xie @ 2019-02-23 13:10 UTC (permalink / raw)
To: Michael S. Tsirkin
Cc: Stefan Hajnoczi, Marc-André Lureau, Daniel P. Berrangé,
Jason Wang, Coquelin, Maxime, Yury Kotov,
Евгений
Яковлев,
qemu-devel, zhangyu31, chaiwen, nixun, lilin24, Xie Yongji
On Fri, 22 Feb 2019 at 22:54, Michael S. Tsirkin <mst@redhat.com> wrote:
>
> On Fri, Feb 22, 2019 at 03:05:23PM +0800, Yongji Xie wrote:
> > On Fri, 22 Feb 2019 at 14:21, Michael S. Tsirkin <mst@redhat.com> wrote:
> > >
> > > On Fri, Feb 22, 2019 at 10:47:03AM +0800, Yongji Xie wrote:
> > > > > > +
> > > > > > +To track inflight I/O, the queue region should be processed as follows:
> > > > > > +
> > > > > > +When receiving available buffers from the driver:
> > > > > > +
> > > > > > + 1. Get the next available head-descriptor index from available ring, i
> > > > > > +
> > > > > > + 2. Set desc[i].inflight to 1
> > > > > > +
> > > > > > +When supplying used buffers to the driver:
> > > > > > +
> > > > > > + 1. Get corresponding used head-descriptor index, i
> > > > > > +
> > > > > > + 2. Set desc[i].next to process_head
> > > > > > +
> > > > > > + 3. Set process_head to i
> > > > > > +
> > > > > > + 4. Steps 1,2,3 may be performed repeatedly if batching is possible
> > > > > > +
> > > > > > + 5. Increase the idx value of used ring by the size of the batch
> > > > > > +
> > > > > > + 6. Set the inflight field of each DescStateSplit entry in the batch to 0
> > > > > > +
> > > > > > + 7. Set used_idx to the idx value of used ring
> > > > > > +
> > > > > > +When reconnecting:
> > > > > > +
> > > > > > + 1. If the value of used_idx does not match the idx value of used ring,
> > > > > > +
> > > > > > + (a) Subtract the value of used_idx from the idx value of used ring to get
> > > > > > + the number of in-progress DescStateSplit entries
> > > > > > +
> > > > > > + (b) Set the inflight field of the in-progress DescStateSplit entries which
> > > > > > + start from process_head to 0
> > > > > > +
> > > > > > + (c) Set used_idx to the idx value of used ring
> > > > > > +
> > > > > > + 2. Resubmit each inflight DescStateSplit entry
> > > > >
> > > > > I re-read a couple of time and I still don't understand what it says.
> > > > >
> > > > > For simplicity consider split ring. So we want a list of heads that are
> > > > > outstanding. Fair enough. Now device finishes a head. What now? I needs
> > > > > to drop head from the list. But list is unidirectional (just next, no
> > > > > prev). So how can you drop an entry from the middle?
> > > > >
> > > >
> > > > The process_head is only used when slave crash between increasing the
> > > > idx value of used ring and updating used_idx. We use it to find the
> > > > in-progress DescStateSplit entries before the crash and complete them
> > > > when reconnecting. Make sure guest and slave have the same view for
> > > > inflight I/Os.
> > > >
> > >
> > > But I don't understand how does the described process help do it?
> > >
> >
> > For example, we need to submit descriptors A, B, C to driver in a batch.
> >
> > Firstly, we will link those descriptors like:
> >
> > process_head->A->B->C (A)
> >
> > Then, we need to update idx value of used vring to mark those
> > descriptors as used:
> >
> > _vring.used->idx += 3 (B)
> >
> > At last, clear the inflight field of those descriptors and update
> > used_idx field:
> >
> > A.inflight = 0; B.inflight = 0; C.inflight = 0; (C)
> >
> > used_idx = _vring.used->idx; (D)
> >
> > After (B), guest can consume the descriptors A,B,C. So we must make
> > sure the inflight field of A,B,C is cleared when reconnecting to avoid
> > re-submitting used descriptor. If slave crash during (C), the inflight
> > field of A,B,C may be incorrect. To detect that case, we can see
> > whether used_idx matches _vring.used->idx. And through process_head,
> > we can get the in-progress descriptors A,B,C and clear their inflight
> > field again when reconnecting.
> >
> > >
> > > > In other case, the inflight field is enough to track inflight I/O.
> > > > When reconnecting, we go through all DescStateSplit entries and
> > > > re-submit the entry whose inflight field is equal to 1.
> > >
> > > What I don't understand is how do we know the order
> > > in which they have to be resubmitted. Reordering
> > > operations would be a big problem, won't it?
> > >
> >
> > In previous patch, I record avail_idx for each DescStateSplit entry to
> > preserve the order. Is it useful to fix this?
> >
> > >
> > > Let's say I fetch descriptors A, B, C and start
> > > processing. how does memory look?
> >
> > A.inflight = 1, C.inflight = 1, B.inflight = 1
> >
> > > Now I finished B and marked it used. How does
> > > memory look?
> > >
> >
> > A.inflight = 1, C.inflight = 1, B.inflight = 0, process_head = B
>
> OK. And we have
>
> process_head->B->process_head
>
> ?
>
> Now if there is a reconnect, I want to submit A and then C,
> correct? How do I know that from this picture? How do I
> know to start with A? It's not on the list anymore...
>
We can go through all DescStateSplit entries (track all descriptors in
Descriptor Table), then we can find A and C are inflight entry by its
inflight field. And if we want to resubmit them in order (submit A and
then C), we need to introduce a timestamp for each DescStateSplit
entry to preserve the order when we fetch them from driver. Something
like:
When receiving available buffers from the driver:
1. Get the next available head-descriptor index from available ring, i
2. desc[i].timestamp = avail_idx++;
3. Set desc[i].inflight to 1
Thanks,
Yongji
^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [Qemu-devel] [PATCH v6 1/7] vhost-user: Support transferring inflight buffer between qemu and backend
2019-02-23 13:10 ` Yongji Xie
@ 2019-02-24 0:14 ` Michael S. Tsirkin
2019-02-24 8:02 ` Yongji Xie
0 siblings, 1 reply; 18+ messages in thread
From: Michael S. Tsirkin @ 2019-02-24 0:14 UTC (permalink / raw)
To: Yongji Xie
Cc: Stefan Hajnoczi, Marc-André Lureau, Daniel P. Berrangé,
Jason Wang, Coquelin, Maxime, Yury Kotov,
Евгений
Яковлев,
qemu-devel, zhangyu31, chaiwen, nixun, lilin24, Xie Yongji
On Sat, Feb 23, 2019 at 09:10:01PM +0800, Yongji Xie wrote:
> On Fri, 22 Feb 2019 at 22:54, Michael S. Tsirkin <mst@redhat.com> wrote:
> >
> > On Fri, Feb 22, 2019 at 03:05:23PM +0800, Yongji Xie wrote:
> > > On Fri, 22 Feb 2019 at 14:21, Michael S. Tsirkin <mst@redhat.com> wrote:
> > > >
> > > > On Fri, Feb 22, 2019 at 10:47:03AM +0800, Yongji Xie wrote:
> > > > > > > +
> > > > > > > +To track inflight I/O, the queue region should be processed as follows:
> > > > > > > +
> > > > > > > +When receiving available buffers from the driver:
> > > > > > > +
> > > > > > > + 1. Get the next available head-descriptor index from available ring, i
> > > > > > > +
> > > > > > > + 2. Set desc[i].inflight to 1
> > > > > > > +
> > > > > > > +When supplying used buffers to the driver:
> > > > > > > +
> > > > > > > + 1. Get corresponding used head-descriptor index, i
> > > > > > > +
> > > > > > > + 2. Set desc[i].next to process_head
> > > > > > > +
> > > > > > > + 3. Set process_head to i
> > > > > > > +
> > > > > > > + 4. Steps 1,2,3 may be performed repeatedly if batching is possible
> > > > > > > +
> > > > > > > + 5. Increase the idx value of used ring by the size of the batch
> > > > > > > +
> > > > > > > + 6. Set the inflight field of each DescStateSplit entry in the batch to 0
> > > > > > > +
> > > > > > > + 7. Set used_idx to the idx value of used ring
> > > > > > > +
> > > > > > > +When reconnecting:
> > > > > > > +
> > > > > > > + 1. If the value of used_idx does not match the idx value of used ring,
> > > > > > > +
> > > > > > > + (a) Subtract the value of used_idx from the idx value of used ring to get
> > > > > > > + the number of in-progress DescStateSplit entries
> > > > > > > +
> > > > > > > + (b) Set the inflight field of the in-progress DescStateSplit entries which
> > > > > > > + start from process_head to 0
> > > > > > > +
> > > > > > > + (c) Set used_idx to the idx value of used ring
> > > > > > > +
> > > > > > > + 2. Resubmit each inflight DescStateSplit entry
> > > > > >
> > > > > > I re-read a couple of time and I still don't understand what it says.
> > > > > >
> > > > > > For simplicity consider split ring. So we want a list of heads that are
> > > > > > outstanding. Fair enough. Now device finishes a head. What now? I needs
> > > > > > to drop head from the list. But list is unidirectional (just next, no
> > > > > > prev). So how can you drop an entry from the middle?
> > > > > >
> > > > >
> > > > > The process_head is only used when slave crash between increasing the
> > > > > idx value of used ring and updating used_idx. We use it to find the
> > > > > in-progress DescStateSplit entries before the crash and complete them
> > > > > when reconnecting. Make sure guest and slave have the same view for
> > > > > inflight I/Os.
> > > > >
> > > >
> > > > But I don't understand how does the described process help do it?
> > > >
> > >
> > > For example, we need to submit descriptors A, B, C to driver in a batch.
> > >
> > > Firstly, we will link those descriptors like:
> > >
> > > process_head->A->B->C (A)
> > >
> > > Then, we need to update idx value of used vring to mark those
> > > descriptors as used:
> > >
> > > _vring.used->idx += 3 (B)
> > >
> > > At last, clear the inflight field of those descriptors and update
> > > used_idx field:
> > >
> > > A.inflight = 0; B.inflight = 0; C.inflight = 0; (C)
> > >
> > > used_idx = _vring.used->idx; (D)
> > >
> > > After (B), guest can consume the descriptors A,B,C. So we must make
> > > sure the inflight field of A,B,C is cleared when reconnecting to avoid
> > > re-submitting used descriptor. If slave crash during (C), the inflight
> > > field of A,B,C may be incorrect. To detect that case, we can see
> > > whether used_idx matches _vring.used->idx. And through process_head,
> > > we can get the in-progress descriptors A,B,C and clear their inflight
> > > field again when reconnecting.
> > >
> > > >
> > > > > In other case, the inflight field is enough to track inflight I/O.
> > > > > When reconnecting, we go through all DescStateSplit entries and
> > > > > re-submit the entry whose inflight field is equal to 1.
> > > >
> > > > What I don't understand is how do we know the order
> > > > in which they have to be resubmitted. Reordering
> > > > operations would be a big problem, won't it?
> > > >
> > >
> > > In previous patch, I record avail_idx for each DescStateSplit entry to
> > > preserve the order. Is it useful to fix this?
> > >
> > > >
> > > > Let's say I fetch descriptors A, B, C and start
> > > > processing. how does memory look?
> > >
> > > A.inflight = 1, C.inflight = 1, B.inflight = 1
> > >
> > > > Now I finished B and marked it used. How does
> > > > memory look?
> > > >
> > >
> > > A.inflight = 1, C.inflight = 1, B.inflight = 0, process_head = B
> >
> > OK. And we have
> >
> > process_head->B->process_head
> >
> > ?
> >
> > Now if there is a reconnect, I want to submit A and then C,
> > correct? How do I know that from this picture? How do I
> > know to start with A? It's not on the list anymore...
> >
>
> We can go through all DescStateSplit entries (track all descriptors in
> Descriptor Table), then we can find A and C are inflight entry by its
> inflight field. And if we want to resubmit them in order (submit A and
> then C), we need to introduce a timestamp for each DescStateSplit
> entry to preserve the order when we fetch them from driver. Something
> like:
>
> When receiving available buffers from the driver:
>
> 1. Get the next available head-descriptor index from available ring, i
>
> 2. desc[i].timestamp = avail_idx++;
>
> 3. Set desc[i].inflight to 1
>
> Thanks,
> Yongji
OK I guess a 64 bit counter would be fine for that.
In order seems critical for storage right?
Reordering write would seem to lead to data corruption.
But now I don't understand what does the next
field do. So it so you can maintain a freelist
within a statically allocated array?
--
MST
^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [Qemu-devel] [PATCH v6 1/7] vhost-user: Support transferring inflight buffer between qemu and backend
2019-02-24 0:14 ` Michael S. Tsirkin
@ 2019-02-24 8:02 ` Yongji Xie
0 siblings, 0 replies; 18+ messages in thread
From: Yongji Xie @ 2019-02-24 8:02 UTC (permalink / raw)
To: Michael S. Tsirkin
Cc: Stefan Hajnoczi, Marc-André Lureau, Daniel P. Berrangé,
Jason Wang, Coquelin, Maxime, Yury Kotov,
Евгений
Яковлев,
qemu-devel, zhangyu31, chaiwen, nixun, lilin24, Xie Yongji
On Sun, 24 Feb 2019 at 08:14, Michael S. Tsirkin <mst@redhat.com> wrote:
>
> On Sat, Feb 23, 2019 at 09:10:01PM +0800, Yongji Xie wrote:
> > On Fri, 22 Feb 2019 at 22:54, Michael S. Tsirkin <mst@redhat.com> wrote:
> > >
> > > On Fri, Feb 22, 2019 at 03:05:23PM +0800, Yongji Xie wrote:
> > > > On Fri, 22 Feb 2019 at 14:21, Michael S. Tsirkin <mst@redhat.com> wrote:
> > > > >
> > > > > On Fri, Feb 22, 2019 at 10:47:03AM +0800, Yongji Xie wrote:
> > > > > > > > +
> > > > > > > > +To track inflight I/O, the queue region should be processed as follows:
> > > > > > > > +
> > > > > > > > +When receiving available buffers from the driver:
> > > > > > > > +
> > > > > > > > + 1. Get the next available head-descriptor index from available ring, i
> > > > > > > > +
> > > > > > > > + 2. Set desc[i].inflight to 1
> > > > > > > > +
> > > > > > > > +When supplying used buffers to the driver:
> > > > > > > > +
> > > > > > > > + 1. Get corresponding used head-descriptor index, i
> > > > > > > > +
> > > > > > > > + 2. Set desc[i].next to process_head
> > > > > > > > +
> > > > > > > > + 3. Set process_head to i
> > > > > > > > +
> > > > > > > > + 4. Steps 1,2,3 may be performed repeatedly if batching is possible
> > > > > > > > +
> > > > > > > > + 5. Increase the idx value of used ring by the size of the batch
> > > > > > > > +
> > > > > > > > + 6. Set the inflight field of each DescStateSplit entry in the batch to 0
> > > > > > > > +
> > > > > > > > + 7. Set used_idx to the idx value of used ring
> > > > > > > > +
> > > > > > > > +When reconnecting:
> > > > > > > > +
> > > > > > > > + 1. If the value of used_idx does not match the idx value of used ring,
> > > > > > > > +
> > > > > > > > + (a) Subtract the value of used_idx from the idx value of used ring to get
> > > > > > > > + the number of in-progress DescStateSplit entries
> > > > > > > > +
> > > > > > > > + (b) Set the inflight field of the in-progress DescStateSplit entries which
> > > > > > > > + start from process_head to 0
> > > > > > > > +
> > > > > > > > + (c) Set used_idx to the idx value of used ring
> > > > > > > > +
> > > > > > > > + 2. Resubmit each inflight DescStateSplit entry
> > > > > > >
> > > > > > > I re-read a couple of time and I still don't understand what it says.
> > > > > > >
> > > > > > > For simplicity consider split ring. So we want a list of heads that are
> > > > > > > outstanding. Fair enough. Now device finishes a head. What now? I needs
> > > > > > > to drop head from the list. But list is unidirectional (just next, no
> > > > > > > prev). So how can you drop an entry from the middle?
> > > > > > >
> > > > > >
> > > > > > The process_head is only used when slave crash between increasing the
> > > > > > idx value of used ring and updating used_idx. We use it to find the
> > > > > > in-progress DescStateSplit entries before the crash and complete them
> > > > > > when reconnecting. Make sure guest and slave have the same view for
> > > > > > inflight I/Os.
> > > > > >
> > > > >
> > > > > But I don't understand how does the described process help do it?
> > > > >
> > > >
> > > > For example, we need to submit descriptors A, B, C to driver in a batch.
> > > >
> > > > Firstly, we will link those descriptors like:
> > > >
> > > > process_head->A->B->C (A)
> > > >
> > > > Then, we need to update idx value of used vring to mark those
> > > > descriptors as used:
> > > >
> > > > _vring.used->idx += 3 (B)
> > > >
> > > > At last, clear the inflight field of those descriptors and update
> > > > used_idx field:
> > > >
> > > > A.inflight = 0; B.inflight = 0; C.inflight = 0; (C)
> > > >
> > > > used_idx = _vring.used->idx; (D)
> > > >
> > > > After (B), guest can consume the descriptors A,B,C. So we must make
> > > > sure the inflight field of A,B,C is cleared when reconnecting to avoid
> > > > re-submitting used descriptor. If slave crash during (C), the inflight
> > > > field of A,B,C may be incorrect. To detect that case, we can see
> > > > whether used_idx matches _vring.used->idx. And through process_head,
> > > > we can get the in-progress descriptors A,B,C and clear their inflight
> > > > field again when reconnecting.
> > > >
> > > > >
> > > > > > In other case, the inflight field is enough to track inflight I/O.
> > > > > > When reconnecting, we go through all DescStateSplit entries and
> > > > > > re-submit the entry whose inflight field is equal to 1.
> > > > >
> > > > > What I don't understand is how do we know the order
> > > > > in which they have to be resubmitted. Reordering
> > > > > operations would be a big problem, won't it?
> > > > >
> > > >
> > > > In previous patch, I record avail_idx for each DescStateSplit entry to
> > > > preserve the order. Is it useful to fix this?
> > > >
> > > > >
> > > > > Let's say I fetch descriptors A, B, C and start
> > > > > processing. how does memory look?
> > > >
> > > > A.inflight = 1, C.inflight = 1, B.inflight = 1
> > > >
> > > > > Now I finished B and marked it used. How does
> > > > > memory look?
> > > > >
> > > >
> > > > A.inflight = 1, C.inflight = 1, B.inflight = 0, process_head = B
> > >
> > > OK. And we have
> > >
> > > process_head->B->process_head
> > >
> > > ?
> > >
> > > Now if there is a reconnect, I want to submit A and then C,
> > > correct? How do I know that from this picture? How do I
> > > know to start with A? It's not on the list anymore...
> > >
> >
> > We can go through all DescStateSplit entries (track all descriptors in
> > Descriptor Table), then we can find A and C are inflight entry by its
> > inflight field. And if we want to resubmit them in order (submit A and
> > then C), we need to introduce a timestamp for each DescStateSplit
> > entry to preserve the order when we fetch them from driver. Something
> > like:
> >
> > When receiving available buffers from the driver:
> >
> > 1. Get the next available head-descriptor index from available ring, i
> >
> > 2. desc[i].timestamp = avail_idx++;
> >
> > 3. Set desc[i].inflight to 1
> >
> > Thanks,
> > Yongji
>
> OK I guess a 64 bit counter would be fine for that.
>
> In order seems critical for storage right?
> Reordering write would seem to lead to data corruption.
>
Actually I'm not sure. If we care about the order, we should not do
access to one block until another access to the same block is
completed?
> But now I don't understand what does the next
> field do. So it so you can maintain a freelist
> within a statically allocated array?
>
Yes, we can use it to maintain a list. The head of the list is
process_head. This list is only used when we want to submit
descriptors in a batch. All descriptors in this batch are linked to
the list. Then if we crash between marking those descriptors used and
clearing their inflight field. We need to find those in-progress
descriptors. The list will be helpful to achieve that. If no batch for
submitting, the next field can be removed.
Thanks,
Yongji
^ permalink raw reply [flat|nested] 18+ messages in thread
end of thread, other threads:[~2019-02-24 8:03 UTC | newest]
Thread overview: 18+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-02-18 10:27 [Qemu-devel] [PATCH v6 0/7] vhost-user-blk: Add support for backend reconnecting elohimes
2019-02-18 10:27 ` [Qemu-devel] [PATCH v6 1/7] vhost-user: Support transferring inflight buffer between qemu and backend elohimes
2019-02-21 17:27 ` Michael S. Tsirkin
2019-02-22 2:47 ` Yongji Xie
2019-02-22 6:21 ` Michael S. Tsirkin
2019-02-22 7:05 ` Yongji Xie
2019-02-22 14:54 ` Michael S. Tsirkin
2019-02-23 13:10 ` Yongji Xie
2019-02-24 0:14 ` Michael S. Tsirkin
2019-02-24 8:02 ` Yongji Xie
2019-02-18 10:27 ` [Qemu-devel] [PATCH v6 2/7] libvhost-user: Remove unnecessary FD flag check for event file descriptors elohimes
2019-02-18 10:27 ` [Qemu-devel] [PATCH v6 3/7] libvhost-user: Introduce vu_queue_map_desc() elohimes
2019-02-18 10:27 ` [Qemu-devel] [PATCH v6 4/7] libvhost-user: Support tracking inflight I/O in shared memory elohimes
2019-02-18 10:27 ` [Qemu-devel] [PATCH v6 5/7] vhost-user-blk: Add support to get/set inflight buffer elohimes
2019-02-18 10:27 ` [Qemu-devel] [PATCH v6 6/7] vhost-user-blk: Add support to reconnect backend elohimes
2019-02-18 10:27 ` [Qemu-devel] [PATCH v6 7/7] contrib/vhost-user-blk: enable inflight I/O tracking elohimes
2019-02-20 19:59 ` [Qemu-devel] [PATCH v6 0/7] vhost-user-blk: Add support for backend reconnecting Michael S. Tsirkin
2019-02-21 1:30 ` Yongji Xie
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